Fix Random Lowercase Letters After Compressing a PDF
Question details
After compressing or optimizing a large PDF document, uppercase text using specific embedded fonts unexpectedly changes to random lowercase letters.
- Product
- PDF Editor
- Device & OS
- not provided
- Scenario
- Reducing the file size or optimizing a 300-page PDF document that contains embedded fonts such as Impact.
- Observed behavior
- Text that originally displayed correctly in uppercase appears as corrupted, random lowercase letters after the optimization or compression process.
Keep a backup copy of your original, uncompressed PDF file to ensure no formatting or data is permanently lost while troubleshooting the compression settings.
Optimize the PDF Without Altering Font Settings
Disabling font subsetting and transparency flattening during compression prevents the software from altering text encoding and rendering.
Advanced PDF optimization tools often attempt to unembed or subset fonts to save space. When dealing with specific fonts like Impact, this process can corrupt the text encoding, causing uppercase letters to render as random lowercase characters.
Open your original, uncompressed PDF in your professional PDF editor and navigate to the 'Save As Other' or 'Optimize PDF' tool.
In the optimization settings dialog, select the 'Fonts' panel and uncheck any options related to unembedding or subsetting fonts.
Navigate to the 'Transparency' panel and choose to keep transparencies intact rather than flattening them.
Save and run the optimization process. Check the newly compressed file to confirm the text remains in its original uppercase format.
Re-export the Original Source Document
If the PDF text is completely corrupted, generating a fresh PDF from the original Word or design file ensures the latest font data is properly embedded.
Update Your PDF Viewer software
Outdated PDF software may contain bugs related to rendering embedded fonts after document optimization.
Safely Compress PDFs with WPS Office
Avoid font corruption and random lowercase letters by using WPS Office to compress your large PDF files securely. WPS PDF Editor intelligently reduces file sizes while strictly preserving your original font encoding and document formatting.
- 1. Open Your PDF: Download and launch WPS Office, then open your uncompressed PDF document.
- 2. Access Compression Tools: Navigate to the 'Tools' tab on the top ribbon and select the 'Compress' feature.
- 3. Select Compression Level: Choose a suitable compression level (such as HD, Normal, or Basic) based on your target file size.
- 4. Compress Safely: Click 'Compress' to reduce the document size while securely keeping your custom fonts fully embedded and readable.
Frequently Asked Questions
Why do random characters appear in my PDF after compressing it?
This typically happens when the compression software attempts to subset or unembed custom fonts to save space. If the process is flawed, the PDF reader misinterprets the font encoding, causing text to display as random or lowercase letters.
How can I check if the Impact font is fully embedded in my PDF?
Open the PDF, press Ctrl+D (or Cmd+D on Mac) to open Document Properties, and navigate to the 'Fonts' tab. Look for the Impact font in the list and ensure it says 'Embedded' or 'Embedded Subset' next to the font name.
Can I reduce a PDF's file size without changing its fonts?
Yes. When using advanced PDF optimization tools, you can manually uncheck font and transparency compression settings. This forces the software to reduce file size purely by compressing images and removing redundant metadata, leaving text untouched.
