Check your file’s exact bytes and calculate a PDFPinch target →
Use the portal’s maximum, not a random quality setting
First check whether the portal gives a byte limit. PDFPinch treats each KB as 1,024 bytes, while a portal may mean 1,000 bytes. For a decimal 1 MB ceiling of 1,000,000 bytes, enter 976 KB: that caps the result at 999,424 bytes. Entering 1,024 KB would allow 1,048,576 bytes and can cause a rejection even though your computer displays “1 MB.”
Choose a byte budget before reducing quality
For a decimal 200 KB limit, 195 KB in PDFPinch allows 199,680 bytes. For a decimal 500 KB limit, 488 KB allows 499,712 bytes. These are conservative conversions, not a guarantee that the portal accepts the document: some also check page count, dimensions, encryption, or file type.
A ten-page document capped at 500,000 bytes has only about 50,000 bytes per page before document overhead. A one-page scan has a much larger detail budget under the same limit. If small text becomes unreadable, the right next step is to change the source scan or permitted page count.
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.
Zoom in on the smallest text, stamps, and identification numbers, then return to normal size to check legibility. Compare the first and last pages with the original, and confirm that no required page is missing. If a QR code matters, test it from the resulting document. A file below the size ceiling can still fail the receiving organization’s quality checks.
If the portal still rejects the file
Read the specific rejection message before compressing again. Check the actual byte size in file properties and verify that you selected the downloaded copy. If size is correct, check the portal’s PDF, password, and page requirements. Repeatedly compressing an already rasterised copy usually sacrifices detail; restart from the original when changing the target.
Updated September 17, 2026. Examples describe PDFPinch’s byte conversion; the destination portal’s published requirements remain the final check.