Why a smaller PDF can be a worse document

Identify the reason for the large file

A PDF made from high-resolution scans is different from a document containing mostly text. Image-heavy pages can often shrink through downsampling and re-encoding. Text and vector drawings are already compact, so applying stronger image settings may do very little to a text-heavy file.

Start with the least destructive option

FOLD’s ordinary compression path targets images while preserving text and vectors. Try this first, then compare the output with the original. Look at small print within scanned pages, signatures, charts and shaded areas. A file that meets an upload limit but cannot be read has not solved the problem.

Understand rasterisation

Aggressive compression turns whole pages into images. This can reduce size in some situations, but it changes the document: text may stop being selectable or searchable, fine lines may become softer and accessibility information can be lost. Consider what the recipient needs to do, especially if they will copy text or search a long report.

Build verification into the workflow

Keep the original, note the destination’s file limit and choose the mildest settings that meet it. Reopen the final download in a PDF viewer and inspect both normal reading size and close-up details. If no useful saving is possible, splitting a submission into permitted sections may be more practical than sacrificing readability.

A worked example: a submission limit

Suppose a portal accepts a maximum of 5 MB and your 12 MB PDF contains scanned attachments. Those numbers are an illustrative example, not a measured FOLD result. Preserve the original, try ordinary image compression and inspect the smallest print on the scans. If the result fits and remains readable, stop there. If it remains too large, consider reducing unnecessary pages or using permitted separate attachments before trying aggressive rasterisation. A receiving system may also impose a page count or file type requirement; meeting the size limit alone is not enough.

What changes and what remains

Mode	Typical target	Trade-off
Ordinary image compression	Images within pages	Image detail can decrease; text and vectors are preserved by the documented path
Aggressive rasterisation	Entire rendered pages	Text becomes image content
Remove unnecessary pages	Document scope	Only appropriate when those pages are not required

Troubleshooting a file that barely shrinks

A text-heavy file may already contain little image data to reduce. A PDF that has been compressed several times may also offer little saving. Check whether the size comes from pages you actually need, and avoid repeatedly applying destructive settings. If the output is blurry, return to the original and choose less aggressive image settings. If the text is no longer selectable, check whether you chose the mode that rasterises the page. Always name the reviewed result separately so that a later edit can start from the best source.