Compress PDF Online Free
Reduce File Size by Up to 90%

The fastest, most reliable way to compress PDF files online without losing quality. Three intelligent compression levels, zero file size limits, and instant download — completely free.

📄Compress PDF Now — It's Free→
90%
Max Size Reduction
∞
No File Size Limit
< 60s
Processing Time
256-bit
SSL Encryption

Quick Answer

Compressing a PDF online means reducing its file size using a web-based tool — no software installation needed. Free online PDF compressors like Scenith analyze the document's content, optimize embedded images, remove redundant data, and apply compression algorithms to shrink the file by 25–90%, while keeping text fully readable and searchable.

How to Compress a PDF Online in 3 Steps

No software to install, no account to create. Compress any PDF file in under a minute — directly in your browser.

⬆️

Upload Your PDF

Drag and drop your PDF into the compressor or click to browse. Any file size is supported — from 1MB invoices to 500MB+ engineering drawings. Password-protected PDFs are also accepted.

Supports: All PDF versions (1.0–2.0), encrypted PDFs
⚙️

Choose Compression Level

Select from three intelligent presets: Low (archives, legal docs), Medium (email, general use), or High (mobile sharing, storage). Or dial in a custom percentage for precise control.

Presets: Low 25–50% · Medium 50–75% · High 75–90%
⬇️

Download Instantly

Processing takes 10–60 seconds depending on file size and complexity. Your compressed PDF downloads automatically. The original is permanently deleted from our servers — your privacy is guaranteed.

Output: Fully searchable PDF · All links preserved

Ready to shrink your PDF right now?

Open Free PDF Compressor →

Which PDF Compression Level Should You Choose?

The right compression level depends on how the PDF will be used, not just on file size. Here's a complete breakdown.

🟢LOW COMPRESSION
25–50% size reduction

Maximum Quality Preserved

Low compression applies lossless optimization — removing invisible metadata, duplicate data streams, and unnecessary structure without touching a single pixel of your images or a single character of text.

This is the right choice when document quality is non-negotiable: legal contracts sent to clients, academic theses submitted to universities, high-fidelity design portfolios, or any document that will be printed professionally.

After Low compression, your PDF looks and reads identically to the original. The only difference is a smaller, faster-transferring file.

Best for:

  • ✓ Legal contracts & NDA documents
  • ✓ Academic theses & dissertations
  • ✓ Medical records & reports
  • ✓ Architectural drawings & blueprints
  • ✓ Professional portfolios

⚠️ Not ideal if you need the smallest possible file — use Medium or High for that.

🟡MEDIUM COMPRESSION
50–75% size reduction

The Everyday Sweet Spot

Medium compression is the most commonly used setting because it delivers a dramatic file size reduction while keeping the document completely professional for on-screen viewing.

Images are resampled to screen-optimized resolution (typically 150 DPI) — imperceptible on monitors, tablets, and phones, but a major factor in file size reduction. Text remains perfectly crisp at all zoom levels.

This is the setting most users need: a report that was 18MB becomes 5MB, small enough to attach to Gmail, upload to Google Drive, or share on Slack — without any visible quality degradation.

Best for:

  • ✓ Business reports & proposals
  • ✓ Email attachments (under 25MB limit)
  • ✓ Presentation decks
  • ✓ Product brochures & catalogs
  • ✓ Invoices & financial statements

⚠️ Not ideal for documents that will be printed at high resolution — use Low instead.

🔴HIGH COMPRESSION
75–90% size reduction

Smallest File, Still Readable

High compression is engineered for situations where file size is the priority above all else: sending PDFs over WhatsApp or Telegram (which has a 100MB limit), uploading to platforms with strict size caps, or storing thousands of archived documents.

Images are compressed aggressively to 72–96 DPI and JPEG quality is reduced significantly. Text and vector graphics remain unaffected — they stay sharp and searchable regardless of compression level.

A 100MB scanned document archive can shrink to under 10MB with High compression. Ideal for mobile consumption where bandwidth and storage are limited.

Best for:

  • ✓ WhatsApp & Telegram file sharing
  • ✓ Uploading to size-restricted portals
  • ✓ Archiving large document collections
  • ✓ Mobile-first document distribution
  • ✓ Reducing cloud storage costs

⚠️ Not suitable for printing or documents with fine image detail that must be preserved.

Real-World Compression Results: What to Expect

Compression results vary by document type and content. Here are representative results across common PDF types:

PDF TypeOriginal SizeAfter LowAfter MediumAfter HighBest Level
Text-only report2 MB1.5 MB1 MB0.6 MBLow
Presentation (images)45 MB30 MB14 MB6 MBMedium
Scanned document80 MB55 MB22 MB9 MBHigh
Invoice / form1.5 MB1.1 MB0.7 MB0.4 MBLow / Med
Product catalog120 MB85 MB38 MB15 MBMedium
Research paper (charts)12 MB8 MB4 MB1.8 MBMedium

*Results are representative estimates. Actual compression depends on PDF structure, image types, and embedded content.

Why Compress PDF Files? The Complete Reasoning

PDF compression isn't just about saving storage. Here's every reason professionals compress PDFs in 2024.

📧

Email Attachment Limits

Gmail, Outlook, and Yahoo all enforce a 25MB attachment limit. A single presentation PDF from PowerPoint can easily hit 40–80MB. Compressing to Medium level almost always brings it under the threshold — without any visible quality loss.

💡 Pro tip: If a compressed PDF is still over 25MB, upload to Google Drive and share the link instead.
☁️

Cloud Storage Costs

Google Drive free storage is 15GB. Dropbox gives 2GB free. If you manage hundreds of PDFs — client files, invoices, reports, contracts — storage fills up fast. Compressing documents to even Medium level can double your effective storage capacity.

💡 Pro tip: Batch-compress old archives to free up cloud space without deleting any files.
🌐

Web & Portal Upload Limits

Government portals, job application systems, university submission platforms, and e-signature tools frequently enforce 5–15MB upload limits. This frustrates users with large documents. Compression eliminates this barrier entirely.

💡 Pro tip: For portals with a 5MB limit, use High compression to safely clear that ceiling.
📱

WhatsApp & Messaging Apps

WhatsApp has a 100MB document limit. Telegram supports up to 2GB. While these limits seem generous, large PDFs drain recipient storage and take minutes to download on mobile data. Compressing to under 10MB makes sharing instant and considerate.

💡 Pro tip: Use High compression for documents shared on mobile — the quality is more than sufficient for reading on phone screens.
⚡

Web Page Load Speed

If your website hosts downloadable PDFs — product manuals, white papers, guides — unoptimized files slow page load times and increase hosting bandwidth costs. Google uses page speed as a ranking factor. Compressed PDFs load faster and improve Core Web Vitals.

💡 Pro tip: Aim for PDFs under 2MB for inline browser viewing, under 5MB for downloadable resources.
🗃️

Long-Term Archival

Organizations archiving thousands of documents — contracts, case files, research papers — face exponential storage growth. Applying Low or Medium compression at ingestion time can reduce archive storage requirements by 40–60% while keeping documents fully accessible and professionally presentable.

💡 Pro tip: Low compression is ideal for archives — you get meaningful size reduction with zero quality trade-off.

How PDF Compression Actually Works: The Technical Breakdown

Understanding the underlying mechanics helps you make better decisions about compression levels for different document types.

1
Stage 1

Metadata & Structure Cleanup

PDF files accumulate invisible overhead: author information, revision history, printer marks, comments, hidden layers, embedded thumbnails, and duplicate color profiles. This metadata can account for 5–20% of total file size. The first compression stage strips all non-essential metadata, reducing file size without any impact on visible content or document functionality.

📊 5–20% size reduction · Zero quality impact
2
Stage 2

Font Optimization & Subsetting

PDFs often embed entire font files even when only a fraction of the characters are used. A full Times New Roman font file is 400–600KB. If your document only uses 80 of the 1,200+ characters in the font, 90% of that font data is wasted. Font subsetting extracts and embeds only the characters actually present in the document — dramatically reducing font overhead while preserving exact typographic fidelity.

📊 5–35% size reduction on text-heavy documents · Identical visual output
3
Stage 3

Image Compression & Resampling

Images are usually the largest contributor to PDF file size. Embedded photos from cameras or design software often contain 300 DPI resolution — far more than necessary for screen viewing (72–96 DPI) or standard office printing (150 DPI). Our algorithm resamples images to the target DPI for your chosen compression level, then re-encodes them with optimized JPEG quality settings. This single stage accounts for 60–80% of the total size reduction achieved.

📊 Up to 80% size reduction on image-heavy PDFs
4
Stage 4

Content Stream Compression

The actual content of a PDF — text positions, drawing commands, path data — is stored as content streams. These streams can be re-encoded using modern compression algorithms (Flate/zlib) for smaller byte footprints. Older or poorly-generated PDFs sometimes have uncompressed or sub-optimally compressed content streams, leaving significant size savings on the table.

📊 3–15% additional reduction on complex PDFs
5
Stage 5

Cross-Reference Table Linearization

PDFs use a cross-reference table that maps each object to its byte position in the file. For optimized "web delivery" (also called linearization or Fast Web View), this table is restructured so the first page can be displayed before the entire file downloads — critical for large PDFs viewed in browser. Scenith's compressor applies linearization automatically, improving perceived loading speed even before bytes are saved.

📊 Faster perceived loading · No additional size reduction

Compress PDF Online: Use Cases by Industry

PDF compression solves real problems across every professional field. Here's how each industry uses it most effectively.

⚖️

Legal & Law Firms

  • →Court e-filing systems cap uploads at 10–20MB. High compression makes large case files compliant.
  • →Contracts sent via DocuSign or Adobe Sign load faster with optimized PDFs, improving client experience.
  • →Client portals used by law firms often have per-file limits. Medium compression keeps documents accessible.
  • →Long-term document retention for 7+ years requires storage efficiency. Low compression is ideal for archival.
🏥

Healthcare & Medical

  • →Patient records shared via secure portals must balance file size with diagnostic image quality.
  • →Research paper submissions to journals have strict size limits — medium compression consistently works.
  • →Clinical trial documentation distributed to investigators needs to be email-friendly without quality loss.
  • →Radiology reports containing embedded scan images can reach 50MB+ — high compression makes them shareable.
🎓

Education & Academia

  • →Thesis submission portals at universities enforce 10–30MB limits. Medium compression is the standard fix.
  • →Research papers with high-resolution figures and charts routinely exceed journal submission file limits.
  • →Lecture notes and course materials distributed to hundreds of students benefit from mobile-optimized sizes.
  • →Academic portfolios for scholarship applications must often stay under 5MB — high compression achieves this.
🏢

Business & Corporate

  • →Annual reports and investor decks are typically 30–80MB. Medium compression makes them email-distributable.
  • →RFP (Request for Proposal) responses with supporting documents must fit procurement portal limits.
  • →Marketing materials updated monthly — brochures, catalogs, price lists — accumulate cloud storage fast.
  • →Board presentations shared via Microsoft Teams or Zoom benefit from fast-loading optimized files.
🏗️

Architecture & Engineering

  • →Technical drawings and blueprints exported from CAD software can reach 200MB+. High compression is essential for sharing.
  • →Building permit applications submitted online frequently have 20–50MB caps per attachment.
  • →Client presentation packages combining renders, plans, and specs need to be emailable.
  • →Low compression is recommended for final archived drawings that may be printed at large format.
🛒

E-Commerce & Retail

  • →Product catalogs with hundreds of item photos are the largest PDFs in retail — compression is critical.
  • →Supplier agreements and purchase orders sent over email must stay under attachment limits.
  • →Customer-facing PDF guides and manuals embedded on product pages affect page load speed and SEO.
  • →Lookbooks and seasonal catalogs distributed digitally should be mobile-optimized for easy browsing.

Compress Your PDF in Under 60 Seconds

No account. No watermarks. No size limits. Just upload, choose a compression level, and download.

📄Compress PDF Free Now→
✅ 100% Free🔒 Files Auto-Deleted⚡ 60-Second Processing📱 Works on Mobile

Frequently Asked Questions: Compress PDF Online

Everything you need to know before compressing your first PDF with Scenith.

How do I compress a PDF online for free without losing quality?

Use Low compression in Scenith's free PDF compressor. Low compression applies only lossless optimizations — metadata removal, font subsetting, and content stream optimization — without touching image quality. The result looks identical to the original but is 25–50% smaller. For most professional documents, this level of reduction is all you need.

Can I compress a PDF to a specific file size, like 200KB or 1MB?

Scenith's tool offers three preset levels rather than a target file size input. However, you can use the High compression level for the smallest possible output. If your document is image-heavy, High compression typically achieves 75–90% reduction. For a 10MB PDF, that means roughly 1–2.5MB output. For very precise size targets, try compressing once, check the output, then consider splitting the document if needed.

Will compressing a PDF make the text blurry or unreadable?

Never. Text in PDFs is stored as vector data (mathematical instructions), not as pixels — so it is completely unaffected by any level of compression. Text remains perfectly sharp, fully searchable, and selectable regardless of which compression level you choose. Only raster images (photos, scanned pages) are affected by compression, and even High compression keeps text in scanned PDFs readable.

Is there a maximum file size for online PDF compression?

Scenith's free online PDF compressor has no maximum file size limit. You can upload PDFs of any size — from 100KB to 1GB+. Processing time will vary: small files (under 10MB) complete in 10–20 seconds, while very large files (100MB+) may take 60–120 seconds. There is no queue or wait time.

Can I compress a scanned PDF without losing the text content?

Yes. Scanned PDFs contain pages stored as images. Compression reduces the size of those embedded images, but the page content remains intact. If your scanned PDF has OCR (Optical Character Recognition) applied, the embedded text layer is completely unaffected by image compression — all searchable text is preserved perfectly.

Does compressing a PDF affect its security or password protection?

Password-protected PDFs can be compressed if you provide the correct password at upload. The compression process maintains password protection on the output file — your document remains secured after compression. If you want to remove password protection during compression, that option is available in the full PDF compressor tool.

How is Scenith's PDF compressor different from Adobe Acrobat's?

Adobe Acrobat's PDF compression requires a $23.99/month subscription (Acrobat Standard) or desktop installation. Scenith's compressor is fully free with no account required. Both tools achieve similar compression ratios using comparable algorithms. Scenith is faster for web-based workflows, while Acrobat offers more granular manual controls for enterprise or print production workflows.

Can I compress multiple PDFs at once?

Currently, Scenith's PDF compressor processes one file at a time to ensure maximum quality per document. For batch compression, simply process files sequentially — each takes 10–60 seconds. The fast processing speed makes sequential compression practical even for large batches.

Are my PDF files safe to upload online?

Yes. All file transfers to and from Scenith use 256-bit SSL/TLS encryption — the same standard used by banks. Your PDF is processed in an isolated secure container on our servers. The original file is permanently deleted immediately after you download your compressed version. Scenith never reads, stores, indexes, or shares your document content.

What happens to hyperlinks, bookmarks, and form fields after compression?

All document functionality is preserved after compression. Hyperlinks continue working, bookmarks (table of contents entries) remain intact, fillable form fields stay interactive, digital signatures are preserved, and internal cross-references are maintained. Compression only affects file size, not document functionality.

People Also Ask About Compressing PDFs

What is the best free PDF compressor online?

Scenith, Smallpdf, and ILovePDF are consistently rated the top free PDF compressors online. Scenith offers no file size limits and making it ideal for quick, one-off compressions. For power users needing batch processing and format conversion, Smallpdf's free tier includes 2 tasks per day.

How do I compress a PDF in Windows 10/11 without software?

The easiest way is to use a free online PDF compressor like Scenith — open your browser, upload the PDF, compress, and download. No software installation needed. Alternatively, Microsoft Word can open and re-save PDFs at a smaller size, though this sometimes alters formatting.

How do I reduce PDF file size on Mac?

Mac's built-in Preview app can compress PDFs: open the PDF, go to File → Export as PDF, then select 'Reduce File Size' from the Quartz Filter dropdown. Results vary widely. For reliable, consistent compression, using Scenith's online compressor typically gives better results with more control.

Can I compress a PDF on iPhone or Android?

Yes — any web-based PDF compressor works on mobile. Open Scenith's PDF compressor in Chrome or Safari on your phone, upload from Files or Google Drive, select your compression level, and download. No app download required. The process is identical to desktop.

Ready to Compress Your PDF?

Join thousands of users who reduce PDF file sizes every day with Scenith's free online compressor. No watermarks. No limits.

📄Compress PDF Online — Free→
✅ 100% Free Forever🔒 256-bit SSL Secure⚡ No Size Limits🗑️ Files Auto-Deleted📱 Works on All Devices
✂️Split PDF🔗Merge PDF🔄PDF to Word🔐Protect PDF🖼️PDF to Image✍️Sign PDF