Compress PDF: a free PDF size reducer

To reduce PDF size, select your PDF above, leave the level on Recommended and press Compress. This PDF size reducer sends back a smaller file with the same pages and the same text, which you can still select and search. Most of the saving comes from the pictures inside the PDF, so a file of photos or scanned pages shrinks the most.

You choose how hard it works. Low only tidies the inside of the file and keeps every picture exactly as it is, so each page looks the same as before. Recommended also saves the pictures again with less detail, and High goes further for the smallest file. For a form with a size limit, pick Target size and set the size instead. Every result is checked before you get it, and if no smaller version passes, your original comes back unchanged.

A picture in a PDF has a resolution: how many dots it holds for each inch of the page (DPI). A photo at 300 DPI is sharp enough to print, but on most screens 150 DPI looks much the same and takes a fraction of the space. Recommended and High use that, and Low does not touch the pictures at all.

In our test, a three-page PDF with a 300 DPI photo on each page went from 3.2 MB to 232 KB at Recommended and 153 KB at High. Low saved under 1%, because it leaves the photos as they are. Black-and-white scans are handled too: two scanned pages at 300 DPI came down to 150 DPI at Recommended and 100 DPI at High, 29% and 42% smaller.

Whichever level you pick, the smaller PDF keeps:

• every page, so the page count is the same;
• all the text, still as text you can select, search and copy;
• the fonts, though at Recommended and High each one keeps only the letters the document uses;
• bookmarks, links and comments.

A result is only released if it opens cleanly, has the same number of pages, still holds the text and is smaller than the file you gave. If none passes, you get your original file back, so a compression can never hand you a broken or bigger PDF.

How much a PDF shrinks depends on what is inside it. Pictures are usually most of the size, so that is where the big savings are. When there is little left to remove, a higher level gains nothing, or the file comes back unchanged:

• It was compressed before. A PDF we had already compressed at High came back unchanged when we tried again, because no smaller version passed the checks.
• Its pictures already hold little detail. A picture at or below the level's DPI is not scaled down, only saved again as a JPEG.
• It is mostly text. Text takes little room, so Recommended and High find nothing more to remove than Low: a 46 KB report saved by a word processor came out at 20 KB at every level.

Made the PDF from photos yourself? Make it again with smaller pictures: when you combine pictures into one PDF, switch off Keep JPGs exactly as they are and pick Smaller under Compress the pictures.

A smaller PDF is not always what you need. To change the words, convert PDF to Word and edit them there. To post a page as a picture, convert PDF to JPG: every page becomes its own JPEG.

Compress PDF also works on a PDF you have just made here. Turn a slide deck into one when you convert PowerPoint to PDF, a saved web page when you convert HTML to PDF, a rich text document when you convert RTF to PDF, or notes when you convert text to PDF. A screenshot works too, once you convert PNG to PDF. Bring the result back to this page if it is too big to send.