How to compress a PDF
Open the tool and choose a PDF file. Pick a level: a little, recommended or most, then choose Compress and save. The smaller copy is downloaded, and the editor shows the size before and after.
What changes
Pictures are saved again as JPEG with no more pixels than their size on the page needs: about 220, 150 or 96 dpi for the three levels. A picture repeated in the file is kept once, objects nothing uses are left out, and the rest is packed more tightly.
What stays
Text, vector drawings, form fields and notes are not changed, so the text stays sharp and can still be searched and copied. If a file cannot be made smaller, you get it back as it was, and the editor says so.