Overview
A smaller PDF is easier to email and more likely to meet an upload portal's limit, but compression is always a tradeoff. The correct target is the smallest file that still supports the reader's task, not simply the smallest number shown after export.
DocuKit's current compressor renders each PDF page to a canvas and places an optimized JPEG of that page into a new PDF. That approach is effective for scans and image-heavy documents, but it changes searchable text and interactive PDF features into page pixels.
Key Takeaways
- Low, Medium, and High describe compression strength: stronger compression uses a smaller render scale and lower JPEG quality.
- The current compressor rasterizes complete pages, so selectable text, links, forms, and vector detail are not preserved as interactive elements.
- Scanned and image-heavy PDFs are the best candidates; archival masters and digitally signed files are poor candidates.
- File-size reduction varies with the source and can occasionally be smaller than expected—or not useful at all.
Step-by-Step Workflow
- Keep an untouched copy of the original PDF and note the receiving service's size limit.
- Upload the file and begin with Low compression when readability or fine detail matters.
- Run the compressor and compare the displayed original and compressed sizes.
- Open the result at 100% zoom and inspect the smallest text, thin lines, signatures, and diagrams.
- Move to Medium or High only if the file is still too large, then repeat the visual check before submission.
What each quality level does
Low uses the highest render scale and about 95% JPEG quality. Medium reduces the render scale and uses about 75% JPEG quality. High produces the smallest page images of the three settings, using the lowest scale and about 50% JPEG quality.
Those percentages are encoding inputs, not a promise of a particular file-size reduction. A PDF that already contains efficiently compressed images may shrink only a little. A large scan assembled from uncompressed photos may shrink much more.
When rasterizing is acceptable
Rasterized output is often acceptable for a read-only scan, a visual proof, or a portal submission that will only be viewed or printed. It is less suitable when someone needs to search, copy text, use screen-reader structure, complete form fields, follow links, or preserve vector artwork.
- Good candidates: receipts, photo scans, signed-paper scans, and visual reference copies.
- Review carefully: resumes, presentations, maps, and documents with small footnotes.
- Avoid for the only archival copy, accessible source documents, forms, engineering drawings, and signed originals.
A practical acceptance test
Check the output in the environment where it will be used. For an email attachment, open it on a phone and a desktop. For printing, print one page containing small text and a photograph. For a submission portal, stay below its limit with a little margin because systems may calculate size differently.
- Compare page count and orientation with the original.
- Zoom into the smallest type and high-contrast edges.
- Confirm that losing selectable text and links is acceptable.
- Keep the original file under a different name.
Frequently Asked Questions
Which compression level should I try first?
Start with Low when quality matters, then move to Medium or High only if the result remains above the required size. Always inspect the new file rather than choosing by the level name alone.
Will text remain searchable after compression?
Not with the current DocuKit method. Each page is rendered as an image, so the visual text remains but the original searchable text layer is not preserved.
Why did my PDF not become much smaller?
The source may already use efficient image compression, contain few images, or be small enough that the new page images and PDF structure offer little savings.
Does compression preserve a digital signature?
No. The result is a newly created PDF and should not be treated as preserving the original file's cryptographic signature or archival status.