An upload form rejects your PDF because it exceeds the size limit. You could remove pages or export everything as a low-resolution image, but either choice may make the document less useful. A better first step is to understand what makes the file large and which changes your reader can accept.
Folio’s Compress PDF tool optimizes the structure of the document. It does not lower image resolution or turn text into page screenshots. That makes it a useful first attempt when you want a smaller file while keeping its existing text and image resolution.
Why PDF file sizes vary so much
Two documents with the same number of pages can have very different sizes. One may contain mostly text and simple shapes. The other may contain a full-resolution scan on every page, plus photographs or other large assets. Page count alone does not tell you how much space a PDF needs.
The way a PDF was generated also matters. Some files contain structural overhead that can be stored more efficiently. Others have already been optimized by the application that created them. A compressor has less room to improve a file that is already compact.
Run a structural optimization
Open Compress PDF and choose the document you want to reduce.
Note the original size and the upload limit you are trying to meet.
Choose Optimize PDF and wait for the operation to finish.
Compare the reported output size with the original. Keep the result that is useful for your destination.
Open the downloaded PDF and review the pages you expect to be hardest to read: small text, charts, screenshots, and scanned details.
Folio rewrites the document using compressed object streams. The aim is to store its structure more efficiently without resampling its images. Existing selectable text is not converted into a picture during this operation. An image-only scan, however, will still be an image-only scan afterward.
Set a useful target instead of chasing a percentage
If an upload accepts files under 10 MB, your practical target is a readable file below that limit. A hypothetical reduction from 11 MB to 9 MB solves that problem. A reduction from 30 MB to 25 MB is larger in absolute terms, but still leaves you needing another step.
These numbers are examples, not promised results. Structural optimization cannot guarantee a specific reduction or a final file size. Folio reports the actual outcome, and an already optimized PDF may stay the same size or become larger when rewritten. In that case, keep the original available.
What to do when the file is still too large
Start with the document’s purpose. If the recipient needs only a few pages, use Split PDF to extract that selection. If the upload accepts multiple files, you may be able to send separate sections. Confirm the recipient’s requirements before splitting a document that must arrive as one complete file.
For an image-heavy PDF, go back to the source when possible. A document prepared for screen reading may not need the same image resolution as a large printed poster. Adjust the image export settings in the original authoring or scanning application, create a new PDF, and inspect the smallest text and fine details before sending it.
Folio’s current compressor does not include image downsampling. Repeatedly running the same structural optimization is unlikely to solve a file-size problem caused mainly by large photographs or scans. Identifying that cause is more productive than running the tool again without changing the input.
Do not confuse a smaller file with a better document
Converting every page into an image may remove useful text selection and other document behavior. Shrinking an image too aggressively can also make small labels difficult to read. Preserve the features your recipient needs and evaluate the result at a normal viewing size, not only as a thumbnail.
Open several pages, including the most detailed page.
Check that text which was selectable in the original is still selectable.
Inspect chart labels, fine lines, and small print.
Compare the final file size with the actual destination limit.
Keep the source PDF so you can choose another export approach later.
Try Compress PDF first. If only part of the document is needed, continue with Split PDF. For a broader preparation workflow, read the guide to merging and organizing PDFs.
Cover photograph by Isaac Smith on Unsplash.
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