A PDF that is too big to email or upload is one of the most common small annoyances. The good news is that you can usually cut a PDF to a fraction of its size without any visible change. This guide explains why PDFs get large, how to shrink one for free, and what to do when it is still too big.
Why is my PDF so big?
Text is tiny. A hundred pages of plain text can fit in a few hundred kilobytes. File size comes almost entirely from three things:
- Images. A scanned document or a photo-heavy brochure stores every page as a large picture. This is the biggest cause by far.
- Embedded fonts. Some files carry several complete fonts, even when only a few letters are used.
- Extra data. Editing history, thumbnails and metadata add up in files that were saved many times.
That is why a 10-page scan can be 20 MB while a 10-page typed report is 100 KB. Compression works mainly by re-saving the images at a lower resolution and cleaning up the rest.
How to compress a PDF online for free
- Open the free Compress PDF tool.
- Upload your PDF (up to 50 MB).
- Choose a compression level (see below).
- Click Compress PDF and download the smaller file.
No account is needed, and there is no watermark.
Which compression level should you pick?
| Level | Best for | What to expect |
|---|---|---|
| Light | Files you will print, contracts, anything with fine detail | High quality, smaller savings |
| Recommended | Most documents: email, uploads, sharing | Text stays sharp, images stay clear, good savings |
| Extreme | Hitting a strict size limit | Smallest file, images look softer |
If you are not sure, start with Recommended. Check the result, and only go to Extreme if the file is still too large for the form or email you need it for.
Common size limits to aim for
Different places have different limits. These are typical, but always check the exact number on the site you are using:
- Gmail: attachments up to 25 MB in total. Larger files are turned into a Google Drive link.
- Job and exam portals, visa and government forms: often 1 MB, 2 MB or 5 MB per document.
- Messaging apps and web forms: frequently 10 MB or less.
Tips to get the smallest file
- Compress once. Running an already compressed PDF through the tool again usually saves very little.
- Scan at a sensible resolution. If you make the scan yourself, 150 to 200 DPI is enough to read text on screen. 600 DPI makes files huge for no visible benefit.
- Remove pages you do not need with Split PDF before compressing. Fewer pages means a smaller file.
- Compress photos before turning them into a PDF. If you are building a PDF from pictures with JPG to PDF, shrink the images first with the Image Compressor.
- Combine after compressing. If you need one file, compress each document first and then join them with Merge PDF.
What if the PDF is still too big?
Some files simply cannot get much smaller, for example a PDF that is already optimized or one that is mostly high-quality photographs. In that case:
- Try the Extreme level.
- Split the file into two parts and send them separately.
- Share a link to a cloud drive instead of attaching the file.
Is it safe to compress a PDF online?
Compress PDF sends your file to our server for processing and deletes it immediately after the compressed version is ready. Nothing is kept. If a document is highly sensitive, you can instead use an offline program on your own computer.
Frequently asked questions
Will compressing a PDF reduce its quality? Light and Recommended keep text sharp and images clear. Extreme can make images look softer, so check the result before you send it.
Does it work on a phone? Yes. Open the tool in your phone browser, choose the PDF from your files, and download the result.
Is there a file size limit? You can upload PDFs up to 50 MB.
Is it really free? Yes, with no sign-up and no watermark.
Compress your PDF now. It usually takes less than a minute.