How to compress a PDF to fit an upload limit
The form says the file can't be larger than a few megabytes and yours is bigger. This guide explains why a PDF gets heavy and how to bring it under the limit.
Why a PDF gets heavy
Text takes almost no space. A ten-page report written in Word usually weighs a few hundred kilobytes. What makes a PDF heavy is images: scanned pages, photos taken with a phone, and graphics exported at high resolution. Each scanned page is a full picture, so a scan of twenty pages can easily weigh more than a hundred pages of text.
That's why compressing works so well on scans and so little on text-only files. Compression lowers the resolution of the images to what's needed to read and print them, and leaves the text as text.
Step by step
- Open aval Workspace and upload the PDF. You can try it without an account.
- If the file is heavy, the inspector says so as soon as it's uploaded and estimates how much it would weigh compressed.
- Choose Compress and pick a level. Start with Recommended.
- Check the new size. If it's under the limit, download it. If not, compress again with Maximum.
- Upload the compressed file to the form. If something looks wrong, the original is still there as an earlier version.
Try it with your own file
aval Workspace is free and works without an account.
Try it free, no accountWhich level to choose
| Level | What it does | When to use it |
|---|---|---|
| Light | Cleans up fonts and the file's structure. Images aren't touched. | PDFs that are mostly text, or when quality matters more than size. |
| Recommended | Takes images to 150 dpi. | Almost always. It's enough to read on screen and to print. |
| Maximum | Takes images to 96 dpi. | Forms with very low limits, when Recommended isn't enough. |
In every level the text stays text. It isn't turned into an image, so it remains sharp and can still be searched and copied.
If it still doesn't fit
- Remove pages you don't need to send. Blank pages from a double-sided scan are common, and the inspector finds them.
- Split the PDF and upload it in parts, if the form accepts more than one file.
- Use Prepare for → For an online form. It recognizes the text of scanned pages and, if the file is over 2 MB, compresses it to the maximum, in one step.
- If you scanned the pages yourself, scan again with good light. Shadows and noise make images heavier.
Mistakes that make it worse
- Compressing the same file many times. After the first pass the gain is small and the images keep losing detail. aval keeps the original instead of giving you a bigger file when compressing doesn't help.
- Printing to PDF from photos of the screen or from a scan. It turns everything into images and the file grows.
- Sending a ZIP. Most forms only accept PDF, and a PDF inside a ZIP barely gets smaller.
Questions
Does compressing a PDF lower its quality?
Only the images, and only above a certain resolution. Light doesn't touch them, Recommended takes them to 150 dpi and Maximum to 96 dpi. Text stays sharp at every level.
Can I get the original back?
Yes. In aval every change is a new version, and the original is always the first one.
What's the largest file aval accepts?
Up to 100 MB per upload, and up to 20 files at a time.
Is it free?
Yes. You can try it without an account; your documents are kept for 24 hours unless you sign in with Google, LinkedIn or GitHub.