Short answer
Open Compress, add a copy of the PDF, start with Quality first or Balanced size, 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.
This guide covers Osenpa PDF Tools. Check requirements and download options before you begin.
On this page
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.
For smaller copies directly from File Explorer, see Reduce PDF and Office File Sizes with Make Smaller. That app uses three profiles and has no target-MB setting; this guide covers the separate PDF Tools workflow.
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
Read the limit in bytes
For an illustrative portal limit of 10,000,000 bytes, a result of 10,100,000 bytes still fails even if a rounded display looks close. In File Explorer, open the file's Properties and check Size, not Size on disk. Leave a margin below the portal limit, then check small text and search or copy a known sentence from the new PDF.
Work toward a practical limit
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Record the real upload limit
Leave a margin below it because portals do not all count file size the same way.
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Start from a copy
Open Compress and add the copied PDF. Choose a separate output folder so the original quality and structure remain available.
You should see: the copied PDF selected while the original stays in its folder.
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Choose a reasonable profile
Start with Quality first or Balanced size. Smaller file is more aggressive. For an eligible single PDF, choose Try a size goal and select one of the offered targets; arbitrary byte values are not an input field.
You should see: the chosen profile and planned output before the job starts.
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Review the output
Select Create compressed copies. Check the reported result, then inspect small text, diagrams, photos, links and forms. Compare the actual file size in bytes with the receiving site's limit.
You should see: a result summary with the achieved size and whether the goal was met. Open any created PDF to verify it.
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 mode works with one PDF at a time. The file must be at least 1 MiB (1,048,576 bytes); the available targets also depend on its analysis and settings. For a batch of PDFs, use a compression profile or process each file separately. 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.