Unrecognized glyphs transform into blank rectangles or generic question marks. Step-by-Step Fixes Across Major Platforms
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7.2 Font Stacks and Fallback Planning
FSO-2026-04 Topic: "Font substitution will occur. Continue?" Issuing Body: Systems Compatibility & Rendering Working Group Date: April 20, 2026
Your readers—and your printer’s wallet—will thank you. Font substitution will occur continue
If you’ve ever opened a PowerPoint presentation, a Word document, or a PDF only to be greeted by the message , you’ve hit one of the most common speed bumps in digital document sharing.
In PDF workflows, font embedding is the most reliable way to prevent substitution. A font can be embedded only if the font vendor permits it. When a font cannot be embedded, Acrobat uses temporary substitution fonts such as AdobeSerifMM for missing serif fonts and AdobeSansMM for missing sans serif fonts. These substitution fonts are designed to stretch or condense to fit, maintaining line and page breaks from the original document. If you share with third parties, their policies apply
: You received a project from someone else but don't have the specific TTF or OTF files installed on your local machine. Glyph Mismatch
: In technical software like GhostScript, substitution can lead to incorrect character rendering if CID mapping doesn't match. How to Fix It How to Fix It