How to Compress a PDF Without Making It Unreadable

Why PDFs get so large

A PDF made from typed text is usually small, often under a few hundred kilobytes. Size grows when the file contains pictures. A scanned document is really a stack of photos, one per page, and a phone scan can easily be several megabytes per page.

Embedded fonts, high resolution photos pasted from a camera, and files that were saved many times can also add weight.

Common size limits you may run into

Many email services limit attachments to around 20 to 25 MB in total. Government portals, job applications and university forms often set tighter limits, such as 1 MB, 2 MB or 5 MB. Check the exact limit on the form before you start, so you know your target.

How to compress a PDF step by step

• Open Compress PDF and add your file.
• Choose a compression level. A lighter level keeps more quality, a stronger level gives a smaller file.
• Press Compress and look at the new size shown next to the original.
• Download the result and open it. Zoom in on a page to make sure small text is still easy to read.
• If it is still too large, run the original again with a stronger level.

Tips to keep the quality

• Start with the lightest level that meets the limit, not the strongest.
• If your PDF is a scan, scan again at a lower resolution, such as 150 DPI, which is enough for reading on a screen.
• Remove pages you do not need first with Remove Pages. Fewer pages means a smaller file.
• Keep your original file. Compression is a one way change.

What to do if the file barely shrinks

A PDF that is mostly text or already optimised has little left to remove, so it may not get much smaller. In that case, split it into parts and send them separately, or share it through a link from a cloud drive instead of attaching it.

Common mistakes when compressing

• Compressing the only copy of a file. Always keep the original.
• Choosing the strongest level straight away, which can make small print hard to read.
• Compressing a file again and again. Each pass can reduce quality further, so go back to the original instead.
• Forgetting to check the result on a phone screen, where blurry text shows up quickly.

A quick way to decide the level

If the limit is only a little below your file size, a light level is usually enough. If you need to go from 20 MB down to 2 MB, you will likely need a strong level, and it is worth checking a few pages closely. For text heavy pages, readability matters more than sharp photographs.

Why PDF files get so large

Most oversized PDFs are large for one reason: the images inside them. A scanned page is a photograph of paper, and a phone scan at full resolution can be two or three megabytes for a single page. Text, by comparison, takes almost no space. A 40 page report that is all text may be only 300 KB, while a 10 page scan can be 25 MB.

Other causes are embedded fonts, pages exported from design software with print quality graphics, and files that were edited many times so that old data is still stored inside. Knowing the cause helps you set your expectations. A text only PDF will barely shrink, while an image heavy PDF can shrink to a tenth of its size.

Common size limits and how to hit them

Email services usually stop attachments at around 20 to 25 MB. Many government portals, job sites and university forms are stricter and ask for 1 MB, 2 MB or 5 MB per document. Start by checking the exact limit, then pick a compression level that gets you safely under it with a small margin, because a file that is 2.01 MB will still be rejected by a 2 MB limit.

• Under 25 MB: a light level is normally enough.
• Under 5 MB: use a medium level and check that text is still crisp.
• Under 1 or 2 MB: use a strong level, and consider splitting the document into parts if it is still too big.

Check the result before you send it

After compressing, open the new file and zoom in on the smallest text, any signatures, stamps and photographs. If a stamp or a handwritten number has become blurry, go back to the original and try a lighter level. It takes a few seconds and can save you a rejected application.

If you only need part of a large document, it can be better to extract the pages you need first and then compress. A smaller starting point means you can keep a higher quality level for the same final size.

Frequently asked questions