Reduce PDF file size
Compression matters only when the result still works. Start by finding what fills the file. Keep the source beside you. Judge the download rather than the size estimate.
Find out what the PDF contains
A digital PDF can contain selectable text, vectors, fonts, forms, links and images. A scanned PDF is usually one large image per page, so two files with the same page count can require different compression methods.
Test text selection, search, zoom and form controls. Check whether photographs or scanned pages account for most of the content before changing the file.
Keep the source file
Save each compression result as a new file. Compression can remove image detail, colour, links, tags, form behaviour or searchable text, depending on the method.
Choose settings for the intended use. Email and quick reading may tolerate more image reduction than print, archiving, accessibility or legal review.
Preserve structure in digital PDFs
Digital PDFs can contain oversized fonts, duplicate resources or inefficient objects. Structure-preserving compression can remove that waste while retaining selectable text, vectors and page geometry.
Rebuild looks for a smaller candidate that preserves PDF structure. If that candidate is not smaller, the tool returns the source instead of a larger file. An efficient PDF may change little.
Compress scanned pages
Scanned and image-heavy PDFs use image recompression to reduce size. Lower resolution and stronger JPEG compression can soften small text, erase light handwriting and add blocks around high-contrast letters. Colour reduction can remove stamps, annotations and pale highlighting.
Start with balanced compression. Use stronger compression only for a sharing copy, and inspect small text at normal size and high zoom. Check photographs, artwork and coloured marks separately from black text.
Check the downloaded PDF
Open the downloaded file instead of relying on the browser preview. Check page count, orientation, dimensions, edges, signatures, table rules, decimal points, footnotes and faint or coloured content.
If the source was searchable, search and copy text from several pages. Test required links and forms. For long or high-stakes documents, compare the beginning, middle and end in another PDF reader.
- Every expected page is present and readable.
- Small text and punctuation remain legible.
- Important colour, signatures and marks are preserved.
- Searchable text, links and forms work where required.
- The result is smaller than the source.
Stop when further compression causes loss
A PDF with efficient fonts and compressed images may have little waste left. Repeated compression can reduce image quality without a useful size reduction. Removing unneeded pages may save more space.
If an attachment limit is too small, split the document into logical parts or use an approved sharing link. Keep the legible source even when it does not meet the limit.
Official sources
Sources checked on 14 August 2026 for the technical and procedural details cited in this guide.