How PDF compression works
Understand why some PDFs shrink and others do not, and choose between structural optimization and image recompression.
Draft prepared: 2026-10-02. Publisher: GXA Technologies. No named expert review is claimed. AI-assisted draft; human editorial review pending
Start with what is inside the PDF
A PDF is a container for page instructions, fonts, pictures and other objects. Two files with ten pages can have very different sizes: one might contain text instructions, the other ten large scanned pictures. Page count alone therefore gives little guidance about compression.
Before choosing a preset, inspect a representative page. Can you select its text? Do photographs or full-page scans dominate? Keep a separate original, especially when forms or digital signatures matter.
What this compressor changes
GXA Toolbox uses qpdf in a browser worker. Low optimizes eligible structure and streams without deliberately recompressing image appearance. Balanced and High can recompress eligible raster pictures; they do not reduce the image pixel dimensions.
Some PDFs are already efficient. A measured no-savings result is preferable to a larger file relabeled as compressed. The tool only offers a compressed download when it is genuinely smaller.
Compare one document, not a promised percentage
Use the same original for each comparison. Try Low first on a text report. For a scan-heavy document, compare Balanced at the same zoom as the original, looking for damaged small characters and artifacts around image edges. Record actual bytes rather than treating the mode name as evidence of savings.
If the result still exceeds an upload limit, remove genuinely unnecessary pages or split the document if the recipient permits multiple files. Neither approach should silently omit required information.
Check more than appearance
Open the saved copy and verify page count, selection of text, links and form behavior. Rewriting a signed PDF normally invalidates its cryptographic signature, even when the visible signature picture remains.
Compression is not privacy cleaning. It does not promise to remove annotations, hidden content, attachments or identifying metadata. Use the appropriate privacy workflow for those concerns.
Report an error in this information
Include the page address and the statement that needs checking. Do not send private files or credentials.