How to Compress a PDF Without Losing Too Much Quality
Published by PdfEdit+ on
To make a PDF smaller, upload it to Compress PDF, pick a compression level, and download the result. The tool rebuilds every page as a JPEG image at a lower resolution, which works well for scanned documents and photo-heavy files.
It is not the right tool for every PDF. Text-based files, such as documents exported from Word, often get larger, and the result has no selectable text. The tool tells you whether your file got smaller or larger, so you can keep whichever version is better. This guide explains why PDFs get big, how to choose a level, and how to check the result before you send it.
Why PDF files get large
Most of a PDF’s size usually comes from images, not text. In general:
- Scanned pages are stored as full-page pictures. A scan made at high resolution or in full colour can take hundreds of kilobytes or more per page.
- Photos and graphics are often embedded at their full original resolution, even when they appear small on the page.
- Text and simple drawings are stored as instructions (letters, lines, shapes) and take up very little space, even across many pages.
So a 3-page scan can be much bigger than a 50-page report that was exported straight from a word processor. Knowing which kind of PDF you have tells you whether compression will help.
How compression trades quality for size
PdfEdit+ draws each page as an image, saves that image as a JPEG, and places it on a page of the same size in a new PDF. Two settings decide the result: the image’s resolution (pixels per inch) and the JPEG quality. Lower values give smaller files, but small text and fine lines get softer.
| Level | What it uses |
|---|---|
| Low | About 108 pixels per inch, JPEG quality 0.85. Sharpest result, least reduction. |
| Medium | About 86 pixels per inch, JPEG quality 0.7. The default; a balance of size and readability. |
| High | About 65 pixels per inch, JPEG quality 0.5. Smallest files; small print can blur. |
Every level rebuilds the pages as images, not just High. The levels only change how much detail those images keep.
How to compress a PDF step by step
- Open Compress PDF and upload one PDF (up to 50 MB). The page shows the file name and original size.
- Choose Low, Medium, or High. Medium is selected to start with.
- Select Compress PDF.
- Read the result line. It shows the new size and either “…% smaller” or “…% larger”. If the file got larger, the page says so and suggests keeping your original.
- Download the file. It is saved as
compressed-followed by your original file name.
Which level should you choose?
Start with Medium, check the result, and adjust. Selecting a different level clears the previous result, so you can try another level on the same file without uploading it again.
- Scanned letters, forms, or contracts: try Medium. If small print is hard to read, use Low.
- Photo-heavy brochures or slides: Medium or High usually gives the biggest savings. Check that faces and charts still look acceptable.
- A file that must fit an email or upload limit: try High, then check readability carefully. If High still isn’t small enough, split the document into parts.
- Text-based PDFs (exported from Word, Google Docs, or similar): compression here will usually make the file bigger and remove the selectable text. Keep the original.
How to check the result
Before you send a compressed PDF, open it and check:
- The smallest text at 100% zoom, such as footnotes, small print, and table numbers.
- Signatures, stamps, and diagrams. Thin lines soften first.
- The page count. It should match the original, and each page keeps its original size.
Also remember what changes when pages become images. You can no longer select, copy, or search the text, and screen readers can’t read it. Links stop working, and fillable form fields are no longer fillable. If any of that matters for the person receiving the file, send the original instead.
Limitations, and when to keep the original
- Text-based PDFs can grow a lot. In our own test, a 3-page text-only PDF grew from about 5 KB to about 470 KB at Medium, because an image of a page is far larger than the text instructions it replaces.
- PDFs that need a password to open can’t be compressed until you remove the password with Unlock PDF.
- One file at a time, up to 50 MB each.