# How to Compress a Scanned PDF Without Making the Text Unreadable

Canonical: https://filevale.com/guides/compress-scanned-pdf-without-making-text-unreadable/
Updated: 2026-11-01

> Shrink a scanned PDF for email or an upload form while the text stays sharp: start from the original, pick a sensible quality and check before you send.

To compress a scanned PDF without making the text unreadable, start from the original scan, compress it once at a moderate quality, and zoom in on the smallest text before you send it. If it still doesn't fit the limit, remove or split pages rather than pushing the quality down until the letters blur. That is the usual trap: a scanned passport or contract is 15 MB, or 300 KB when the form allows 150 KB, and a compressor gets it under the limit but leaves the words fuzzy.

## Why scans get blurry when you compress them

A scanned PDF is a stack of photos of paper, one per page. Compressing it means storing those photos with less detail. Small print, stamps and signatures are the first things to suffer, and every extra round of compression on an already compressed file blurs them a little more. So the order you do things in matters as much as the tool.

## Check what is taking up the space

[Open PDF Size Breakdown](https://filevale.com/size-breakdown/)

Before you compress, open the PDF in PDF Size Breakdown to find out what makes it so big. If one or two pages account for most of the size, you can deal with those pages instead of squeezing the whole document.

## Compress the scan once, from the original

[Open Compress PDF](https://filevale.com/compress-pdf/)

1. Open Compress PDF and choose your original scanned file: drop it on the page or click to browse.
2. Adjust the quality, then click **Compress**. Start in the middle rather than at the lowest setting.
3. Download the PDF and open it. Zoom in on the smallest text, numbers and any signature.
4. If it is still too big, change the quality and run again on the **same original file**, not on the copy you just made.

Compress PDF re-renders each page as a JPEG image, which is why scans shrink well. Text in the result is not selectable, which makes no difference for a scan whose text was a picture to begin with. Everything happens in your browser, and the file is not uploaded, which matters for passports, IDs and contracts.

## If X is the problem

- **The limit is tiny (150 KB or similar) and the scan has several pages.** Send only what is asked for. Remove extra pages with [Delete PDF Pages](/delete-pdf-pages/) or pull out the ones you need with [Extract PDF Pages](/extract-pdf-pages/), then compress.
- **The form accepts several files.** Use [Split PDF](/split-pdf/) to make one file per page, then compress each page on its own.
- **The text is already blurry in the original.** Compression can't bring detail back. Rescan the page: good light, the phone held flat, and your phone's document scanner mode instead of a plain photo. See [how to scan documents into a PDF with your phone](/guides/how-to-scan-documents-into-pdf-with-phone/).
- **You scan on a flatbed scanner.** For text documents, 150–200 DPI in grayscale is usually enough and makes a much smaller file to start with than a 600 DPI colour scan.
- **The PDF is mostly real text, not a scan.** Turning text pages into images can make the file bigger. [How to compress a PDF for email](/guides/compress-pdf-for-email/) covers what to do instead.

## What about Mac Preview?

On a Mac, Preview offers **File → Export** with a *Reduce File Size* Quartz filter. It is built in, but it applies a fixed, aggressive setting, and on scans it often produces exactly the unreadable text you are trying to avoid. A tool with a quality setting you can change gives you more control.

## Frequently asked questions

### Why is my compressed scan still blurry when I raise the quality?

You are probably compressing a file that was already compressed. Each pass discards detail that can't be recovered, so go back to the first scan you made and compress that one, once.

### Can I make the text in a scanned PDF searchable?

Not with the Filevale website: that needs OCR, which the browser tools don't do, and [PDF to Text](/pdf-to-text/) only reads PDFs that already contain a text layer. The Filevale for iPhone app includes document scanning with on-device OCR.

### Is it safe to compress a passport or ID scan this way?

Compress PDF runs inside your browser and the file never leaves your device, so it is not sent to a server. Keep the original scan somewhere safe in case you need a sharper copy later.