The file names its fonts instead of carrying them, so each reader substitutes whatever it has. Check the Fonts tab in the document properties: an entry without "(Embedded)" beside it is being substituted. The fix is to re-export from the original with fonts embedded — it cannot be repaired in the PDF.
1Check what the file actually carriesOpen the document properties and look at the Fonts tab. Each entry says "(Embedded)" or "(Embedded Subset)" — anything without that is being substituted on your machine.
2Confirm it is not just your computerOpen it on another device or in a browser. If it looks right there, the fonts are missing and that machine happens to have them installed.
3Re-export from the original with embedding onIn Word, this is the "Embed fonts in the file" option; in most design software it is a PDF export preset. This is the real fix.
4If you no longer have the original, convert from a copy that renders correctlyExporting to PDF from a machine that has the fonts installed produces a file with them embedded.
5For anything that must travel, stick to common facesA document set in a widely available typeface survives a missing-font situation with its layout intact.
Why does this happen?
The fonts were never embedded. The exporter referenced them by name to keep the file small. On a machine without those fonts, the reader picks a substitute and every line length changes with it.
Only a subset was embedded. Most files embed just the characters used. Add text later — in a form field or an annotation — and characters outside that subset have nothing to draw with.
The characters are outside the font’s range. Boxes or question marks where symbols, accents or non-Latin text should be mean the font has no glyph for them.
The encoding table is missing or wrong. A badly produced file can embed a font without the map from glyph to character. It displays correctly but copies as gibberish.
A licensed font was blocked from embedding. Some commercial fonts carry flags that forbid embedding, so the exporter leaves them out.
Questions
Can I embed fonts into an existing PDF?
Not reliably, and not here. Embedding requires the font file itself and the license to include it; a PDF that omitted a font does not contain enough to reconstruct it. Re-exporting from the source document is the dependable route.
Why does my PDF show boxes instead of letters?
The font being used has no glyph for those characters — common with symbols, mathematical notation, accented letters and non-Latin scripts. The document needs a font that covers them, chosen in the original.
Why did my layout shift on someone else’s computer?
Because a substituted font has different letter widths, so every line breaks in a new place and tables stop lining up. Embedding prevents it entirely.
How do I know a PDF I am sending will look right?
Check the Fonts tab before sending: every font should say Embedded or Embedded Subset. That is the whole test, and it takes a few seconds.