Compress PDF Online
Reduce PDF file size without losing quality. Choose from multiple compression levels to optimize your documents for email, web upload, or storage. Fast and secure.
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Max file size: 100MB • Accepted: .pdf
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Compress PDF Online — Smaller Files, Same Document
A 30MB PDF won't attach to a Gmail message (25MB limit), gets rejected by Outlook (20MB), and crawls when you upload it to a portal or website. Our free online PDF compressor fixes that in seconds: it downsamples oversized images, re-encodes them efficiently, and strips redundant data so your file shrinks dramatically while the layout, text and fonts stay exactly as designed. No software to install, no watermark, and nothing to sign up for.
Smart Image Downsampling
The compressor finds the heaviest images, lowers their resolution to a screen-friendly DPI and re-encodes them — where 90% of PDF bloat hides.
Three Compression Levels
Pick Maximum for the smallest size, Recommended for the best size-to-quality balance, or Minimum for lossless, print-ready output.
Text Stays Selectable
Unlike "print-to-image" shrinkers, we preserve the text and font layers, so your compressed PDF remains searchable, copyable and accessible.
Color & Vector Safe
Embedded ICC color profiles and vector line art are kept intact, so logos, charts and brand colors print accurately after compression.
How to Compress a PDF in 3 Steps
- Upload your PDF — drag the file onto the upload box, or click Select PDF to pick it from your device, Google Drive or Dropbox.
- Choose a compression level — tap the Maximum, Recommended or Minimum card. The preview shows the estimated new file size before you commit.
- Compress and download — click Compress PDF, wait a few seconds, then download the smaller file or save it straight back to cloud storage.
Which Compression Level Should You Choose?
Every level keeps text and vector content lossless — the difference is purely how aggressively images are reduced. Use this table to decide:
| Level | Typical reduction | How it works | Best for |
|---|---|---|---|
| Maximum | up to 80% | Downsamples images to ~96–120 DPI with stronger lossy JPEG re-encoding | Email, chat, quick sharing, storage |
| Recommended Most popular | 40–60% | Downsamples images to ~150 DPI — visually identical on screen | Most documents with mixed text and images |
| Minimum | 20–30% | Lossless stream (Flate) compression only — no image data discarded | Print shops, portfolios, presentations, contracts |
How PDF Compression Actually Works
Most PDFs are far larger than they need to be because design software embeds images at full camera or scanner resolution — often 300–600 DPI — when a screen only renders about 96–150 DPI. Our compressor reduces file size through several complementary techniques:
- Image downsampling — high-resolution images are scaled to a sensible target DPI, the single biggest saving in almost every PDF.
- Lossy re-encoding — photos are re-saved with optimized JPEG quality; line art and screenshots use lossless encoding to stay crisp.
- Font subsetting & de-duplication — only the glyphs you actually use are kept, and fonts embedded multiple times are merged.
- Object & stream compression — the underlying object streams are Flate-compressed and duplicate objects are removed, following the ISO 32000 PDF specification.
- Metadata cleanup — orphaned bookmarks, unused form data and bloated XMP metadata are trimmed away.
Compressing Scanned PDFs
Scanned documents are the heaviest PDFs of all because every page is a full-resolution image with no text underneath. They also compress the most — typically 60–80% smaller at the Recommended or Maximum level. If your scan already has an OCR text layer, compression preserves it, so the file stays searchable. Need to combine several scans before shrinking them? Run them through our Merge PDF tool first, then compress the single combined file for the best result.
Tips to Get the Smallest PDF
A few habits squeeze out the most size without hurting quality:
- Start with Recommended. It clears email and upload limits for most files while staying visually identical. Only step up to Maximum if you still need it smaller.
- Compress after merging, not before. Combining first lets the compressor de-duplicate shared fonts and images across the whole document in one pass — merge your PDFs first.
- Delete pages you don't need. Dropping blank scan backs or cover sheets with Delete Pages can cut size before you even compress.
- OCR scans before compressing if you need to search them — running OCR after lossy compression produces worse text recognition.
- Keep the original. Lossy compression is permanent, so archive the full-resolution copy if you may reprint at high quality later.
Why Compress PDF Files?
Smaller PDFs are easier to live with everywhere. They slip under email attachment caps (Gmail 25MB, Outlook 20MB), upload to job portals, government forms and content systems without timing out, load faster when embedded on a web page (which also helps your own site's Core Web Vitals), and take up a fraction of the space in cloud storage and backups. For businesses sending proposals, invoices or contracts at scale, compression cuts bandwidth and speeds up every download your customers make.
Frequently Asked Questions
Does compression affect digital signatures?
Yes — rewriting the file invalidates an existing digital signature because the signed bytes change. Compress first, then sign. Drawn signatures and stamps are unaffected.
Can I compress a scanned PDF?
Yes, and scans shrink the most (often 60–80%) since each page is an image. Any OCR text layer is kept, so the document stays searchable.
Will my embedded fonts and text survive?
Yes. Fonts are subsetted, not removed, and the text layer stays fully selectable and searchable — your compressed PDF remains accessible.
Is compression reversible?
No. Maximum and Recommended permanently discard image data, so keep your original if you might need full resolution. Minimum is lossless.
Can I compress password-protected PDFs?
Enter the password for protected files, or remove it first with our Unlock PDF tool, then compress.
Does it work on my phone?
Yes — the compressor runs in any modern browser on iPhone, Android, Mac and Windows, with no app to install.
How much smaller will my PDF be?
Image-heavy and scanned PDFs usually shrink 50–80%; text-heavy documents 20–40%. The preview shows the estimated result before you download, so there are no surprises.
Is the PDF compressor free and private?
Yes — free with no registration for files up to 50MB (Pro raises this to 500MB). Uploads are encrypted in transit and automatically deleted after 30 minutes.