How to subset fonts in a pdf to reduce file size
- Step 1Upload the PDF with embedded fonts — Drop the document into the font subsetter.
- Step 2Apply font subsetting — The tool removes all unused characters from each embedded font.
- Step 3Download the subset PDF — Save the optimised file.
- Step 4Verify text appearance — Confirm all text renders correctly in the subsetted PDF.
Frequently asked questions
How much size reduction can font subsetting achieve?+
For documents using large CJK (Chinese, Japanese, Korean) fonts, subsetting can reduce the font data by 95%+. For Latin fonts with limited character use, typically 30-60% reduction.
Will subsetted fonts cause issues if the PDF is edited later?+
Yes — if you edit text in a subsetted PDF and add characters not in the subset, those characters will display as placeholders. Subset only final, uneditable PDFs.
Is font subsetting the same as font embedding?+
No — embedding includes the full font; subsetting embeds only the characters used in the document. Both produce a self-contained PDF, but subsetting produces a smaller file.
Privacy first
All PDF processing runs locally in your browser using PDF-lib and pdf.js. No file is ever uploaded — only metadata counters are saved for signed-in dashboard stats.