Compress PDF
Reduce PDF file size while maintaining readability. Choose from Low, Balanced, or High quality presets.
Drop files here or click to upload
.pdf · Max 20 files
Or paste files with Ctrl+V
Your files never leave your browser
What is PDF Compress?
Compress PDF shrinks a PDF by rendering every page and re-encoding it as a JPEG image at a lower resolution. Three presets set the target: Low (72 DPI), Balanced (108 DPI) and High (144 DPI). This reliably reduces scanned and image-heavy documents, with one important trade-off — the output pages are pictures, so text in them is no longer selectable or searchable.
How to use PDF Compress
- Drop one or more PDF files (up to 20 at a time).
- Pick a quality preset — Balanced (108 DPI) is the recommended default for on-screen reading.
- Click "Compress" — pdf.js renders each page to a canvas and pdf-lib repackages the JPEGs into a new PDF.
- Compare original vs compressed size and download the result.
Why use AinnoBox for this
- All three presets stay at or above 72 DPI, so pages remain legible on screen instead of collapsing into the mush that aggressive compressors produce.
- You see the before and after byte count for every file, so you can decide whether the saving justifies the quality drop.
- Batch up to 20 documents in one run, each processed and reported independently.
- Rendering happens in a Web Worker on your device — the pages of a confidential report are never rasterised on someone else's hardware.
- Free and unlimited, with no account and no watermark on the compressed file.
PDF Compress — frequently asked questions
- Why can I no longer select text after compressing?
- Because compression works by rendering each page to a bitmap and embedding that image in a new PDF. This is what makes the saving predictable on scanned documents, but it does mean text becomes part of the picture. If you need selectable text, keep the original and compress a copy only for sending.
- Which preset should I choose?
- Balanced (108 DPI) for anything that will be read on a screen. High (144 DPI) when the document may be printed or viewed on a Retina display. Low (72 DPI) only when you need the smallest possible file and legibility at normal zoom is enough.
- My text-only PDF got bigger instead of smaller. Why?
- A PDF that is pure vector text is already extremely compact — converting those crisp glyphs into JPEG pictures costs more bytes than it saves. Compression pays off on scans, photos and slide decks, not on text documents exported from a word processor.
Want to understand why AinnoBox processes everything in the browser rather than on servers? Read How It Works or check the FAQ.