How to compress a PDF without losing quality

A 23 MB PDF. A 10 MB email attachment limit. You’ve been here before.

The fix is compression, but the word “compression” makes people nervous. Nobody wants to send a client a blurry document. Here’s how to shrink a PDF and keep it looking sharp.

Where the file size actually comes from

Open any PDF and look at what’s inside: text, vector graphics (lines, shapes, logos), and raster images (photos, scanned pages, screenshots).

Text and vectors are tiny. A 50-page text document with no images might be 200 KB. The moment you embed a single high-resolution photo, the file jumps to several megabytes.

PDF compression targets those embedded images. It re-encodes them at a lower resolution and higher JPEG compression. Text and vectors pass through untouched.

The three presets and what they actually do

Preset	Typical reduction	What changes	Best for
High	10-30% smaller	Light re-encoding, images stay sharp	Print-quality documents
Medium	40-60% smaller	Noticeable re-encoding at 200% zoom, fine at 100%	Email, screen reading
Low	60-80% smaller	Photos visibly softer, text stays crisp	Archival, max compression

Start with Medium. It’s the right tradeoff for 90% of use cases. If the result looks fine, you’re done. If photos matter, switch to High.

How to compress

Open the PDF compressor
Drop your file
Pick a preset
Check the before/after sizes and download

The tool shows both sizes so you can decide on the spot. If you’re not happy, try a different preset. Nothing is saved or uploaded.

When compression won’t help

Text-heavy PDFs: If your document is mostly text with a few small diagrams, it’s already compact. Compression might shave off 5-10%, not 50%.
Already-compressed PDFs: If someone already ran compression before sending it to you, a second pass won’t do much.
Password-protected PDFs: Some encrypted PDFs can’t be re-encoded without the owner password.

When compression helps the most

Scanned documents: Every page is a full-resolution image. A 20-page scan can easily be 40 MB. Compression brings it down to 5-10 MB.
Presentations exported as PDF: Slide decks with photos on every page are image-heavy by nature.
Reports with embedded charts and screenshots: These tend to embed images at higher resolution than needed for on-screen viewing.

Privacy

The compression runs in your browser using WebAssembly. Your PDF never leaves your device. There’s no upload, no server-side processing, and no account to create.

How to convert HEIC to JPG (when the problem is format, not size)
MOV vs MP4: what’s the difference (video files have the same compatibility vs. size tension)