PDF size has several causes
A PDF can contain text, fonts, vector paths, photographs, scanned pages, forms and metadata. No single setting can reduce all of them without trade-offs. This tool focuses on how the document objects are stored rather than lowering image resolution.
The tool re-saves compact objects
The browser loads the document and writes it with PDF object streams enabled. That can remove inefficient structural overhead in some files. It does not rasterize pages or deliberately reduce embedded image quality, so a scan dominated by JPEG images may barely change.
The smaller file wins
Re-saving can occasionally increase a document. The tool compares the actual byte counts and keeps the original when the candidate is not smaller. The status explains this instead of presenting a larger file as successful compression.
When another approach is needed
A scan may need image downsampling or optical character recognition. A design export may need font subsetting or different source settings. Those tasks require more control and can affect quality, searchability or accessibility, so they are outside this lightweight browser tool.
Private local processing has limits
The PDF stays in browser memory and is not uploaded. Encrypted, damaged or unusually complex files may not load. Keep the original and open the downloaded result before relying on it, especially when forms, signatures or specialised PDF features matter.
Measure success with the real output
A compression button should not imply improvement when no bytes were saved. This tool reports the input and output sizes and returns the original when structural rewriting produces a larger candidate. Open the result and search, zoom and print a representative page before sharing it. If the document is still too large, return to the source application and export with suitable image resolution, font embedding and quality settings. That route usually gives better control than repeatedly processing a finished PDF. Confidential documents should also be handled according to the organisation's storage and retention rules, even when processing is local.
What the three choices mean
Smallest file accepts any smaller structural result. Balanced keeps the original when the saving is below two percent. Best quality keeps the original bytes unchanged. These are decision rules around the measured output, not image-resolution presets. Meaningful image downsampling would need a separately reviewed PDF engine and could affect readability.