Merging, splitting and shrinking PDFs on your own device

A PDF is a collection of pages, and each page refers to the fonts, images and drawing instructions it needs. Most everyday PDF jobs (merging, splitting, reordering, rotating) only rearrange those pages. That is why they can be done quickly in your browser without changing how the pages look.

Merging and splitting

Merging copies pages from several files into a new one, along with the resources they use. Splitting does the reverse. With page ranges you can pick exactly what you need: 1-3, 4-10, 11-end turns a 12-page file into three files of 3, 7 and 2 pages. The PDF merger and splitter does this with page thumbnails so you can check the order.

Things that do not always survive: bookmarks (the outline), links between documents, and form fields with the same name in different files.

Rotating and reordering

Rotating a page in a PDF usually just changes the page's rotation setting; the content is untouched and nothing is re-rendered. Use the page organizer for scans where one page came out upside down.

Why some PDFs shrink and others don't

Almost all of a large PDF's size is usually images: photos in a brochure, or every page of a scan. Compressing a PDF means recompressing those images at a lower resolution or quality while leaving text and vector graphics alone, so the text stays sharp and selectable.

A PDF that is mostly text is already small. Compressing it achieves little, and anyone promising a 90 % reduction for every PDF is either rasterizing pages (turning text into pictures) or exaggerating. The PDF compressor shows the before and after size so you can decide.

Scanned documents

A scanned PDF is a stack of photographs of paper. It has no text layer, so you cannot search it or copy text from it, and text extraction finds nothing. OCR (optical character recognition) reads the text in the images; the OCR tool can add an invisible text layer so the PDF becomes searchable while looking exactly the same.

For the best OCR results, scan at 300 DPI, straight, with good contrast.

Passwords and signatures

• Password-protected PDFs must be unlocked (with the password) before their pages can be rearranged.
• Changing a digitally signed PDF invalidates the signature. Do page operations before signing.
• A drawn signature added with an annotation tool is an image, not a certificate-based digital signature.