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Two modes - pick the one that fits the job

Make a PDF small enough to actually send

Scanned documents and image-heavy brochures shrink the most. Choose the mode, set the resolution, and the new file is written in your browser - nothing is uploaded, no account, no watermark.

Short answerLast edited October 31, 2026

The PDF Compressor shrinks a PDF by re-encoding the images inside it at a resolution and quality you choose, and it keeps the text selectable. A 40 MB scan typically becomes a few megabytes, because most of a scanned file is image data.

3resolution levels (110 / 150 / 200 dpi)
40-90%image quality range
0bytes uploaded

There is no free lunch, only a choice

Most heavy PDFs are heavy for one reason: pictures. A scanned contract is a photo of paper, a product brochure is a set of large images, a slide deck exported as PDF is a wall of gradients. Text, by contrast, costs almost nothing - a hundred pages of plain text can fit in a few hundred kilobytes.

So there are two honest ways to make a PDF smaller, and they give up different things. Rasterising re-renders every page as a JPEG at the resolution you pick. Files drop dramatically - often by 70 to 90 percent on scans - but the text becomes part of the picture: it cannot be selected, searched or copied, and a screen reader can no longer read it. Optimising rewrites the file structure and compresses the streams while keeping text as text. The gain is smaller and depends on how the PDF was produced; files that were already optimised barely move.

Choose rasterising for scans, signed copies, portfolios and anything that only has to be read. Choose optimising for invoices, contracts, forms and documents that an archive or a portal will parse, where selectable text matters more than the last hundred kilobytes.

It helps to know where the weight sits before choosing. A PDF built from Word is mostly text and fonts: a few hundred kilobytes for dozens of pages, and compressing it changes almost nothing. A PDF produced by a scanner is one large image per page: the same document becomes ten or twenty megabytes, and rasterising at a lower resolution is the only lever that matters. A brochure sits in between - vector text over large photos - and responds well to rasterising at 150 dpi if nobody needs to copy the text out of it.

Pick a resolution
  • 110 dpi - smallest file, fine for a phone screen
  • 150 dpi - the safe default for reading and printing at A4
  • 200 dpi - small print and signatures stay crisp
  • Above 200 dpi the file grows fast with little visible gain
  • Text documents gain nothing from rasterising

What each setting does to the result

The tool reports the real before and after size on every run
ModeTextTypical resultUse it for
Optimiseselectablesmall gain, sometimes nonecontracts, invoices, archives
Raster 110 dpian imagemuch smallerquick reading copies, portals with 2 MB limits
Raster 150 dpian imagesmaller, still sharp on A4scans you may print again
Raster 200 dpian imagemoderate gainsignatures, small print, stamps

The run, in three moves

1

Decide what matters

Does anyone need to search, copy or fill the text? If yes, optimise; if no, rasterise.

2

Set resolution and quality

150 dpi at 70% is a good first try for a scan. Raise it only if small text is unreadable.

3

Compare and download

The result row shows the exact before and after size. If the gain is small, try one step lower.

Honest answers about PDF compression

Why did my PDF barely shrink in optimise mode?
Because it was already efficient. Optimising rewrites structure and compresses streams; if the producer (Word, LaTeX, a scanner app) already did that, there is little left. The images inside are untouched, and they are usually the weight. Switch to rasterising if the file has to be smaller.
Can I keep the text and still get a big reduction?
Only partly, and not in a browser. Keeping text while recompressing the images needs a full PDF processor that re-encodes each embedded image in place. The honest trade here is: text stays, size barely moves; size drops, text becomes a picture.
Is a compressed PDF still legally valid?
For reading and archiving, generally yes. For anything that depends on a digital signature or on form fields, no: rasterising removes the signature layer and the fields. For signed documents use optimise, or keep the original alongside the compressed copy.
What is the best setting for a scanned contract?
150 dpi at 70% is usually readable and much smaller. If the scan contains small print, stamps or handwriting, try 200 dpi at 75% and compare the two results - the tool shows both sizes, so the choice takes a minute.
Does compression change the page size or orientation?
No. Each page keeps its width, height and orientation; only the content inside is re-encoded. A landscape page stays landscape and an unusual size such as a receipt roll stays that size, which matters when the file is printed again.
Does the file leave my computer?
No. The PDF is opened and re-written in the browser tab: pdf.js draws the pages, the PDF library assembles the new file. Nothing is sent to a server.

A 12 MB scan can be a 900 KB file

Pick a mode, run it, check the numbers. If it is still too big, go one step lower.

Compress my PDF

Quick facts

  1. Most of a scanned PDF is images, which is why downsampling those images shrinks the file far more than any other setting.
  2. Compressing images only leaves the text layer and the links editable; flattening the pages would destroy both.
  3. A PDF describes every element by its position on the page, which is why it looks identical everywhere and why its text does not reflow.Adobe
  4. PDF 2.0 permits AES-256 encryption for the password that protects a document, while older files may use 40-bit RC4.Adobe
  5. JPEG splits the picture into 8×8 pixel blocks and stores a discrete cosine transform of each block, which is where its block-shaped artefacts come from.ITU-T

Questions people ask

How do I make a PDF smaller for email?
Choose a compression level that lowers the image resolution, usually to 150 dpi for screen reading, and export. Check the file size and the readability of small text. Many email services accept up to 20 to 25 MB, but smaller is more reliable.
Does compressing a PDF reduce quality?
It reduces the image quality. Text stays sharp only if it is stored as text. Scanned pages are images, so text in them softens as the resolution falls. Choose the least compression that gives a file size you can send.
Why is a scanned PDF so much bigger than a text PDF?
A scan stores each page as a photograph, which takes far more data than a page of characters. A text PDF uses a few kilobytes per page, while a colour scan can use a megabyte or more per page.

What this page is about

  • PDF

    The Portable Document Format, standardised as ISO 32000 and documented by Adobe in the PDF 1.7 reference, that fixes the layout of a page.

  • JPEG

    A lossy still-image format standardised as ITU-T T.81 in 1992 and still the default format of most cameras and phones.

  • PNG

    A lossless image format defined by the W3C with an 8-bit alpha channel and gamma information, designed for the web in 1996.

  • OCR

    Optical character recognition: turning the pixels of a scanned page into selectable text, done in the browser by Tesseract compiled to WebAssembly.

Official sources cited on this page

  1. PDF 32000-1:2008 — Document management, Portable Document FormatAdobe
  2. Recommendation T.81: Digital compression and coding of continuous-tone still imagesITU-T
  3. PNG (Portable Network Graphics) Specification, Third EditionW3C
  4. Tesseract OCR engine documentationTesseract OCR project

Continue with the same file

Each of these opens what the tool above produces. Use “Use in another tool” under the result to carry the file over — it moves from tab to tab inside your browser, never to a server.

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Switched-off tools are not listed here: only what works right now.

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