There is no universal compression percentage. A text document behaves differently from a high-resolution scan, and an already optimised PDF may not become meaningfully smaller.
PDFUAE exposes three clear levels. Light compression focuses on file structure, while stronger modes may rasterise pages. The right choice depends on whether size, print quality or searchable text matters most.
Choose the right compression level
Confirm the upload limit
Check the recipient's maximum size first. Aim to get safely below that limit instead of chasing the smallest possible file.
Start with light compression
Use this when searchable text, copying or print clarity matters. Move to the next level only if the result remains too large.
Use balanced compression for screen reading
This can suit routine attachments, but inspect stamps, signatures, tables and small text after processing.
Treat strong compression as a last step
Choose it for strict limits, then review important pages carefully because resolution and text search may be reduced.
What to inspect after compression
The final size is below the upload limit
Small text and stamps remain legible
Images have no obvious artefacts
Every page is present and ordered
Search and copy still work when required
When compression is not the best answer
The PDF has unnecessary pages
Removing them before compression often saves more space without reducing quality.
The recipient accepts separate files
Splitting a document into logical attachments may be clearer than applying aggressive compression.
The PDF is already optimised
There may be little room to improve. An honest result can be no useful reduction without visible quality loss.