When the PDF Optimizer seems to misbehave, the cause is usually one of two things: something stopped the tool from running, or it ran but the result is not usable. This guide starts with the fastest checks, then walks through the common problems and exact fixes.
Quick Checks First
- Refresh the page - a stalled session is the most common cause of nothing happening.
- Confirm the input is not empty and actually contains what you meant to submit.
- Try the smallest possible input; if that works, the issue is size, not the tool.
- Turn off browser extensions that block scripts, then reload and test again.
- Update or switch browsers if the problem repeats across sessions.
Common Problems and How to Fix Them
Savings are modest
Text-dominant PDFs are already lean - most weight lives in images, which the image compressor targets directly.
A font renders differently after optimising
Font subsetting kept only used characters - embedded custom fonts may need re-embedding for edits later.
Something broke in an old reader
Choose the compatibility priority so output stays conservative for legacy software.
My signature no longer validates
Optimising alters the file - sign after optimising, never before.
I ran it three times
Diminishing returns plus re-encoding risk - once from the original is the right workflow.
Links stopped working
That should not happen - re-run without cleanup priorities, or repair the source document.
When It Works but the Output Is Poor
If the tool runs fine but the result misses, the problem is almost always the brief, not the software:
- Optimizing an already signed document
- Expecting dramatic savings on text-only files
- Optimizing repeatedly
- Ignoring compatibility priority for old readers
How to Stop It Happening Next Time
- Keep a saved prompt template for every task you repeat.
- Change one setting per generation so causes stay obvious.
- Run a two-minute sanity test with known input after any update.
- Note every failure and its fix; a short troubleshooting log pays for itself.
Still Stuck?
Reproduce the problem with the smallest possible input and note the exact steps that triggered it. A one-line description of what you did, what you expected and what happened is enough to get a precise answer from support or a colleague.
Frequently Asked Questions
What does optimising actually change?
It removes redundant objects, streamlines fonts and re-encodes images while preserving visible content.
Is optimising safe for signed documents?
No - any file change invalidates digital signatures. Optimise before signing.
How is this different from compression?
Compression targets weight primarily; optimisation also cleans structure and improves delivery behaviour.
Is my file uploaded?
No - everything runs entirely in your browser.
Related Guides
- How to Use PDF Optimizer
- What Is a PDF Optimizer and How Does It Work?
- PDF Optimizer Examples: Real Scenarios and Results
- PDF Optimizer for Office Workers and Web Publishers
- Best PDF Optimizer Alternatives Worth Trying
- PDF Optimizer Tips and Best Practices
- Is PDF Optimizer Safe? Free vs Paid
- More PDF optimization tools and guides