How to compress a PDF without ruining it

What makes a PDF big

Almost always it is pictures. Text and simple vector graphics are tiny, so a hundred pages of plain text can be well under a megabyte. One full-resolution photo can be several megabytes on its own. A scanned document is the extreme case, because every page is a photograph of a page.

That is why two PDFs with the same number of pages can differ in size by a huge margin, and why a long contract can be smaller than a three-page brochure.

Check what you have first

Open the file and try to select a sentence with your mouse. If the text highlights, it is mostly real text, and there is not much to squeeze. Compression tools work on the images inside a PDF, not on the text. If you can’t select anything, it is a scan, and you will see the biggest savings.

Pick the right level

Compress PDF has three presets, and the names are a fair description:

• Recommended is a sensible default for most documents. Start here.
• Extreme trades image sharpness for the smallest file. It suits email attachments and forms where legibility matters more than looks.
• Near-lossless is for PDFs with photos or detailed drawings that you don’t want to see softened.

Compression makes a new, smaller copy. Your original is not touched, so it is always safe to try a stronger setting and compare.

If it is still too big

1. Cut what you don’t need. A cover sheet, a blank back page or an appendix nobody asked for all count. Remove PDF Pages takes them out in a few clicks.
2. Compress with Recommended, then look at the result. Zoom in on the smallest text before you decide it is good enough.
3. Step up to Extreme only if you still need to. Check the pages again.
4. Split it. If one file must stay sharp and still has to get through, Split PDF can cut it into parts, by page count or by a target size.
5. Go back to the source. If you made the PDF yourself, export it again at a lower image resolution. Squeezing afterwards can only do so much.

Mistakes that cost quality

• Compressing a compressed file. Each pass throws away a little more detail, and the gains shrink quickly. Always work from the original.
• Expecting miracles from a text PDF. If it is already small, there is little to gain. That isn’t the tool failing.
• Deleting the original. Keep it, especially for anything you may need to print at full quality later.

What counts as small enough?

It depends on where the file is going. Many email services cap attachments somewhere around 20 to 25 MB, and some work or school accounts set lower limits. Government and job portals often ask for a specific size, sometimes as low as a couple of hundred kilobytes. Check the limit first, so you know what you are aiming for.

A note on privacy

Compress PDF runs in your browser. The file is not uploaded, which is handy when the PDF is a contract, a medical report or a bank statement. The flip side is that your device does the work, so very large files take longer, and there are size limits: 100 MB per file on a computer and 50 MB on a phone.