PDF producers often carry only the characters a document uses from each font, so a letter the document never needed may not be in the file. When you type one, something has to draw it: in PDF Textfix, the fallback font, never picked silently.

In what order does PDF Textfix choose a fallback font?

When the line’s own font already has the character, no fallback is needed. Otherwise PDF Textfix looks in this order and takes the first that can draw it:

  1. another copy of the same font in the file, such as a second subset of the same typeface;
  2. the same font installed on your Mac;
  3. the closest standard font.

The order keeps the new character close to the line’s design.

Where do you see a fallback font?

  • On the line. A character drawn with a fallback font is orange. One from another copy of the line’s own font is underlined. A red character means no font in the document or on your Mac can draw it; when a close character exists, Edit > Use Suggested Character (⌃⌘U) types it.
  • In the editor bar, which names the fallback and, under it, the line’s own font.
  • In the Issues pane (⌥⌘I), as a numbered line that “uses a fallback font”, with “fallback: Times-Bold” under it.
The editor bar of PDF Textfix under a line being edited. It reads: Characters in orange are drawn with another font (fallback: Times-Bold). Below it, the font line: Font: IBMPlexSerif-SemiBold (embedded subset), 20 pt.
The editor bar names the fallback font and, under it, the line's own font.

The screenshot comes from the demo cover letter, written without “é”: its subsets lack it, so correcting “Renee” to “Renée” draws it in Times-Bold, the closest standard font. The orange is a mark in the editor, not a color written into the file.

What does a fallback font add to the file?

One more font object. PDF Textfix never changes a font already in the document: the new characters go into a font added for the text you inserted, and every other character keeps its original font. After the save, Document Properties or pdffonts lists that added font next to the document’s own.

In a PDF/A file, the fallback is always embedded in the saved file, never a standard font referenced only by name. When an embedded font’s licence restricts its use, PDF Textfix never builds a new font from it; the character comes from another face or the edit is refused with the licence as the reason.

How do you avoid or check a fallback font?

  • Install the line’s typeface on your Mac, if you have a licence for it. When the installed copy matches the one in the file (the same widths, a TrueType file that allows embedding), step 2 takes the character from it and keeps the design; otherwise step 3 applies. You are responsible for the licence of fonts you installed.
  • Check the line before you save. The orange or underlined characters show which ones a fallback draws.
  • Compare the font lists. Run pdffonts (from Poppler, brew install poppler) on the original and on the saved copy:
pdffonts original.pdf
pdffonts edited.pdf

The saved copy also lists the font added for the text you inserted, and every font of the original is still there.

  • Read the Issues pane (⌥⌘I) before you send the file: it lists every line whose edit used a fallback font.

PDF Textfix is free to try on your own documents from the download page.

Questions about fallback fonts

Is a fallback font the same as font substitution in a viewer?

No. A viewer substitutes a font the document does not embed, for all of that font’s text, in that viewer only, on screen and in print, without changing the file; Adobe notes that “The substitution cannot always match the shape of the original characters”. A fallback font draws only the characters you typed, and it is saved in the file.

Why is one letter orange while I edit?

The line’s font lacks that letter, so a fallback font draws it; the editor bar names the font.

Does a fallback font change the rest of the line?

No. Only the characters that need it use it.