When to compress a PDF

A PDF that will not send is usually large because of pictures, not because of the words. Compressing it is the right move when those pictures can be smaller and the text must stay selectable. It is the wrong move when the file is large because it contains many pages you do not need, or because it is already a scan of a printed page.

Compress, split, or leave it

Compress when one document has to travel as one file and the pictures inside it are heavier than the page needs. A slide deck exported to PDF, a report with full-size photos, and a brochure saved for print are the usual cases. Compress PDF rewrites those pictures at a lower resolution and leaves the text as text.

Split when the size comes from pages you can remove. A 40-page scan where you only need pages 3 through 6 should be cut, not squeezed. Split PDF writes the pages you keep. Merging first and then compressing is backwards if the extra files were never meant to be in the packet. Merge PDF is for files that belong together.

Leave the file alone when it is already small, when it is a signed or certified PDF, or when a recipient has asked for the original export. Compression changes the pictures. A contract that was digitally signed should be sent as it was signed.

What the quality preset changes

Smallest aims at screen reading. Pictures are reduced the most. Balanced, the default, is the level meant for email and uploads. High keeps more of the picture for a page someone may print. The words, fonts, and drawings stay as they are at every level. A page that is only text often barely shrinks, because there is no picture to shrink.

If the PDF is a scan, the "text" is a picture of text. Compression can make that picture muddy, and it will not become real text. Export a cleaner scan, or keep the original, instead of running the smallest preset twice.

You can turn each page into an image with PDF to JPG when a form only accepts pictures. That is a different job from compression: the result is no longer a PDF, and the text is no longer selectable.

Before you upload

Remove the password first. A locked PDF cannot be opened here. Check that you are allowed to send the file. Guest downloads last 30 minutes after the job finishes, then the files are deleted. A signed-in account keeps them for 24 hours, and your conversions can run the same tool and the same quality preset again while those files are still stored.

If the job fails, the page shows a short reason and a reference. Send the reference from the support page. Related PDF tasks are compared on the PDF hub.