Upload your PDF and compress it instantly. Decrease file size up to 70% while maintaining visual quality.
Drop your PDF here to compress it
Click to browse or drag & drop
TL;DR — Compress a PDF in 15 seconds
Three steps. Under 15 seconds. Files never leave your browser.
Click Browse or drag and drop your PDF into the upload zone. Works on desktop, iPhone, or Android — supports files up to 150 MB.
Select Low (30-40% smaller), Medium (50-60%, recommended), High (20-30%, print quality), or Extreme (70-80% smaller) — plus Smart or Max Compression mode.
Click Compress PDF and your smaller file downloads instantly. No watermarks added, no sign-up required — compress as many times as you need.
Why PDFcrest
No daily limits, no watermarks, no signup — just instant, high-quality PDF compression.
Compress PDF file size by up to 90% without sacrificing readability. PDFcrest's dual-mode engine (Smart + Max Compression) picks the optimal strategy automatically for your document type.
Most PDF compressions complete in under 30 seconds, even for multi-hundred-page documents. Smart compression runs partially in your browser so small files compress almost instantly.
Compress PDF free online with no daily limit, no account, and no subscription. Unlike SmallPDF or ilovePDF which cap free users at 2 tasks/day, PDFcrest is always unlimited.
Compress PDF on iPhone, iPad, Android, or desktop — no app needed. PDFcrest's mobile-optimised interface makes reducing PDF file size effortless on any screen.
Choose Low, Medium, High, or Extreme compression, each with real quality/size tradeoffs — plus two engine modes: Smart or Max Compression.
All uploads use TLS encryption. Your PDF is processed in an isolated environment and permanently deleted after download. PDFcrest never stores, reads, or shares your document.
Comparison
| Feature | PDFcrest | Adobe Acrobat Online | SmallPDF / ilovePDF |
|---|---|---|---|
| Compress PDF — Free | ✓ Always free | ✗ Limited free tier | ✗ 2 tasks/day |
| No Signup Required | ✓ Zero signup | ✗ Adobe account | ✗ Email required |
| No Watermarks | ✓ Never | ✓ | ✗ Free adds watermark |
| Multiple Compression Levels | ✓ 4 levels + 2 modes | ~ Basic | ~ Limited |
| Works on iPhone | ✓ Mobile-first | ✓ App required | ✓ |
| File Deleted After Download | ✓ Immediately | ~ Varies | ~ 1 hour |
Use Cases
From students to enterprises — everyone needs to reduce PDF file size at some point.
Compress PDF for email to stay under size limits. Most email clients cap attachments at 10–25 MB. PDFcrest reduces even large scanned reports to under 5 MB without visible quality loss.
Reduce PDF size before uploading to university portals. Many learning management systems cap uploads at 5–10 MB. Compress your assignment or thesis without affecting readability.
Shrink proposals, invoices, and reports before sharing with clients. Compressing PDF files speeds up loading for recipients on slow connections and reduces cloud storage costs.
Reduce PDF file size online before embedding in a website or linking from a landing page. Smaller PDFs load faster, reducing bounce rate and improving Core Web Vitals.
Government portals and court filing systems often enforce strict file size limits. Compress PDF free to meet these requirements without losing document integrity or text searchability.
Compress PDF on iPhone or Android before sending via WhatsApp, Telegram, or iMessage. Mobile messaging apps restrict file sizes — a compressed PDF shares instantly without quality compromise.
Workflow Recipes
Compression is rarely the last step. Here are the tool combinations PDFcrest users chain together most often.
Converted a Word document to PDF? Compress the result before emailing it, since DOCX-to-PDF exports often carry oversized embedded images.
Combine multiple PDFs into one document first, then compress the merged file once instead of compressing each part separately.
If a compressed file is still over a portal's upload limit, split it into smaller parts and submit each one separately.
Once a sensitive document is small enough to email, add a password before sending it to a client or colleague.
Need a thumbnail or preview image of a compressed report? Convert its pages to JPG after shrinking the file.
Technical Detail
When you compress a PDF file, PDFcrest uses one of two strategies depending on your selection. Smart Compression re-encodes embedded images at reduced quality, removes duplicate font subsets and unused resource streams, and applies Deflate stream compression to object data — all without rasterising the page, so the output PDF remains fully text-searchable and copy-paste-compatible.
Max Compression mode converts each page to a high-quality JPEG image and repackages them into a new PDF. This approach achieves the highest file size reduction — often 85–90% — and is ideal for scanned documents, image-heavy presentations, or any PDF where text searchability is not required.
After compression, the resulting PDF is standards-compliant and compatible with all major PDF viewers — Adobe Acrobat, Preview (Mac), Chrome, Firefox, and mobile PDF apps. You can further merge compressed PDFs or split them by page range using PDFcrest's free tool suite.
Under the Hood
No black box — these are the literal JPEG quality and max-dimension values this page applies to every embedded image, per level and per engine.
Smart Compression (object-level image re-encode):
level = low → quality = 0.85, maxDimension = 2048px
level = medium → quality = 0.65, maxDimension = 1200px (recommended)
level = high → quality = 0.92, maxDimension = 3000px (print quality)
level = extreme → quality = 0.40, maxDimension = 800px
Max Compression (rasterise each page, then re-embed as JPEG):
level = low → scale = 2.0, quality = 0.85
level = medium → scale = 1.5, quality = 0.65
level = high → scale = 2.5, quality = 0.90
level = extreme → scale = 1.0, quality = 0.40
| Level | What it actually does |
|---|---|
low | Re-encodes images at 85% JPEG quality, capped at 2048px on the longest side — visually near-identical to the original, ~30-40% smaller. |
medium | 65% quality, capped at 1200px — the recommended default, balancing size and readability at ~50-60% smaller. |
high | 92% quality, capped at 3000px — despite the name, this is the highest-quality, lowest-reduction setting ("print quality"), for cases where source fidelity matters more than size. |
extreme | 40% quality, capped at 800px — the most aggressive setting, for scans and image-heavy files where searchability and fine detail aren't needed. |
FAQ
Answers to the most common questions about compressing PDF files
References & Further Reading
Page last updated: · Written and maintained by the PDFcrest team. The compression settings shown above are taken directly from the code running on this page.