Your source document used Garamond. The converted PDF uses Times New Roman. Or your branded sans-serif became Helvetica. The typography is wrong.
What's actually going wrong
Conversion engines need access to the source fonts to embed them in the PDF. If the source app didn't embed them, or the converter doesn't have them, substitution happens.
Licensed commercial fonts often can't be embedded by third-party converters. Open-source fonts (Google Fonts) embed freely. System fonts vary by OS.
The quick fix
Use Flint's converter which handles font embedding more aggressively than most tools.
For source-based conversions, ensure 'embed all fonts' is enabled at the source app's export step. In Word: File > Options > Save > Embed fonts in file. In Pages: similar option in export dialog.
If that didn't work
If fonts can't be embedded due to licensing, the choices are: use a different font that can be embedded, license a version of the font that allows embedding, or convert text to outlines before export (making text shapes — visually identical but no longer editable).
For universal compatibility, use standard system fonts (Helvetica/Arial, Times/Cambria, Courier) — they're available on every system.
Prevent it next time
Use embeddable fonts. Embed at source export. Convert with Flint. Test on multiple viewers and machines.
FAQ
Can I embed any font in a PDF?
Legally, only fonts whose licence permits embedding. Technically, most tools warn or refuse when fonts can't be legally embedded.
What happens if a font can't be embedded?
The viewer substitutes a fallback font. The substituted font might look similar or noticeably different. Either way, your original typography isn't what the recipient sees.
Are Google Fonts embeddable?
Yes — Google Fonts are open-source with embedding permitted. Safe choice for documents that need to look consistent.
Does converting to outlines hurt quality?
No — text becomes mathematical shapes that render identically at any zoom. Downside: no longer selectable, searchable, or editable. Useful for final-output documents.
Embed fonts at source. Use Flint for conversions. Test before distributing.