Short answer
Add a copy of the PDF, choose a compression option, and create a new file. Compare the new size with the upload limit, then open the result and check that it is still easy to read.
When to use this method
Compression can reduce many PDFs by changing image and document settings. An already optimized source will not reach a much smaller limit unless you accept lower visual quality or remove content.
What you need before compressing a PDF
- A copy of the PDF
- The exact file-size limit from the receiving website or person
- A small amount of room below that limit
Work toward a practical limit
Record the real upload limit
Leave a margin below it because portals do not all count file size the same way.
You should see: a clear target that is slightly smaller than the real limit.
Start from a copy
Keep the original quality and structure available.
You should see: the copied PDF selected while the original stays in its folder.
Choose a reasonable profile
Use the least aggressive option that has a chance of meeting the limit.
You should see: the chosen profile and planned output before the job starts.
Review the output
Check the reported size, then inspect small text, diagrams, photos, links and forms.
You should see: the exact result size and a new PDF that opens normally.
If the result is too large or loses needed behavior
Try the next stronger profile only after reviewing a copy. Stronger reduction trades image quality and interactive-feature preservation for a smaller file. Inspect both after every attempt. If the document is already optimized, split it into accepted parts or ask the receiver for another transfer method instead of making text unreadable.
Target-size choices appear only when the combined input is at least 1 MiB. Encrypted PDFs are skipped, so use an unencrypted copy that you are authorized to change.
Compression mistakes
- Promising an exact final size
- Judging quality from the file size alone
- Discarding the original before the receiving system accepts the result
Compressed PDF checkpoint
- The file's actual byte count is below the real upload limit, or the app clearly reports that it is above the limit.
- Representative pages remain readable at normal zoom, and required links, forms and searchable text still work.
- If quality or required behavior fails, keep the source and use a less aggressive profile or another transfer method.
Osenpa PDF Tools
Try quality-first, balanced, strong or eligible target-size compression locally and review the reported bytes and visible result.