Use the portal’s maximum, not a random quality setting
If the upload box says “maximum 1 MB,” set 1 MB as the ceiling. A result slightly below that limit usually preserves more detail than choosing a generic “strong compression” preset.
Why some PDFs shrink easily
A PDF made mostly from vector text can already be efficient. A scan or phone-photo PDF stores large page images and usually has far more room to shrink. Page count, colour, resolution, and image noise all affect the final size.
What PDFPinch changes
When the original is already below the target, PDFPinch returns it unchanged. When substantial compression is required, it renders each page and rebuilds the document using compressed page images. It tests several quality and resolution levels to find a readable result under the requested ceiling.
Know when not to rasterise
Rebuilding pages as images can flatten selectable text, hyperlinks, form fields, layers, accessibility tags, and digital signatures. Do not use that method for signed contracts, archival originals, interactive forms, or documents that must remain searchable.
If the target is impossible
A 40-page colour scan may not remain readable at 100 KB. Raise the limit if the portal allows it, remove unnecessary pages, scan in greyscale, or split the document only when the destination accepts multiple files.
Check the download before submitting
Open the compressed PDF, inspect every page at normal zoom, confirm the page order, and check the final size shown by the upload portal. Always keep the original document.