Text that changes font between your screen and someone else's is not a mystery. It is a file that did not bring its fonts with it.
Embedded versus referenced
A PDF referencing a font says "render this in Helvetica Neue Light". If the reader has it, the page looks right. If not, the reader picks something else and the page does not.
An embedded font is different: the glyph outlines travel inside the file. The page renders identically on a machine that has never heard of the typeface, which is the entire promise of the format.
Embedding costs size — a full font family is a few hundred kilobytes per weight. Subsetting embeds only the characters actually used, which usually costs tens of kilobytes and is what you want in nearly every case.
Diagnose it in two clicks
Open document properties — File, then Properties — and look at the Fonts tab. Every font in the document is listed, and each says whether it is embedded and whether it is a subset.
| What it says | Meaning |
|---|---|
| Embedded Subset | Ideal — glyphs travel, size stays small |
| Embedded | Fine — the whole family is in the file |
| (nothing after the name) | Not embedded — will substitute elsewhere |
| Type 3 | Bitmap glyphs; prints poorly, does not scale |
| A name you do not recognise | Already substituted, on your machine |
That last row is worth pausing on. If the Fonts tab lists a typeface you never used, substitution has already happened. What you are looking at is not what the author saw.
The symptoms and what they mean
- Different typeface on another machine. Not embedded. The classic case.
- Lines reflow or overlap. The substitute has different character widths, so a line that fitted no longer does.
- Boxes, or nothing, instead of characters. The substitute lacks those glyphs — common with non-Latin scripts, currency symbols and dingbats.
- Text is fine on screen, wrong when printed. The printer is doing its own substitution. Your machine has the font; the printer does not.
- Spacing looks slightly loose or tight throughout. A metrically similar substitute, which is the hardest version to notice and the easiest to ship.
- Copy and paste produces gibberish. A subset embedded without a proper character map — the glyphs display correctly but carry no encoding.
That last one surprises people because the page looks perfect. The text is there, it renders, and it copies out as nonsense — which also means search does not find it and a screen reader announces noise.
Fixing it at the source
Embedding has to happen when the PDF is created. You cannot reliably add a font to an existing PDF, because the file records positions calculated with the original metrics — substituting the real font back in does not restore the layout the author intended.
- Word. File → Options → Save → tick "Embed fonts in the file". Leave "Embed only the characters used" ticked to keep the size down, and untick "Do not embed common system fonts" if the recipient may be on a different OS.
- Excel and PowerPoint. Same dialog, same setting, and it is off by default in more versions than it is on.
- Google Docs. Always embeds on export. Nothing to configure.
- InDesign and Illustrator. Embedded by default, but check the licence — some fonts prohibit embedding, and the export will silently outline or substitute instead.
- Print to PDF. Usually embeds, but the setting lives in the driver rather than the application, and varies by driver.
If the source is gone and the PDF has the wrong fonts, the honest options are to accept it, or to rasterise the pages with PDF to JPG so the appearance is frozen. Rasterising costs the text layer, so it is a last resort rather than a fix.
Fonts and file size
Fonts are a real contributor to size and one people rarely check.
A full CJK font family is several megabytes because it carries thousands of glyphs. Embedding four weights of a Latin family is around a megabyte. Subsetting typically takes that to tens of kilobytes, because a document uses perhaps eighty distinct characters.
So a document that looks like plain text and weighs several megabytes may be carrying unsubsetted fonts rather than hidden images. Re-exporting with subsetting on usually fixes it outright — the wider diagnosis is in why is my PDF so big.
Choosing fonts that travel well
If a document will be edited by other people, or printed somewhere you do not control, the typeface choice is a practical decision rather than only an aesthetic one.
- Safest: the metric-compatible classics — Arial, Helvetica, Times New Roman, Courier. Present essentially everywhere, and substitutions between them barely shift.
- Good: open-licence families such as the Google Fonts library. Embedding is permitted without question and they are widely available.
- Check the licence: many commercial fonts restrict embedding, and some forbid it entirely. The export may then silently outline the text, which stops it being selectable.
- Riskiest: a font installed only on your machine. It will look right for you and for nobody else.
Frequently asked questions
Why does my PDF look different on another computer?
The fonts were referenced rather than embedded, so the other machine substituted what it had. The substitute has different character widths, which is why lines reflow and text overlaps rather than simply looking different.
How do I check whether fonts are embedded?
File then Properties, and open the Fonts tab. Every font is listed with its status. "Embedded Subset" is ideal. A name with nothing after it is not embedded. A typeface you never used means substitution has already happened on your own machine.
Why is my text showing as boxes?
The substituted font does not contain those glyphs. It is most common with non-Latin scripts, currency symbols and dingbats — the reader has a font, just not one with the characters your document needs.
Can I embed fonts into an existing PDF?
Not reliably. The file records glyph positions calculated with the original metrics, so putting the real font back does not restore the intended layout. Embedding has to happen when the PDF is created; re-export from the source.
Why does copied text come out as gibberish?
The font was subsetted without a proper character map. The glyphs render correctly, so the page looks perfect, but they carry no encoding — which also means search finds nothing and a screen reader announces noise.
Do embedded fonts make the file much bigger?
Unsubsetted, yes — roughly a megabyte for four Latin weights and several for a CJK family. Subsetting embeds only the characters actually used, usually tens of kilobytes. A text-only PDF weighing several megabytes is often carrying unsubsetted fonts.