Which PDF editors keep the original font?

In their own help pages, four of the seven vendors tie keeping the original font to having it installed on your computer. Adobe says that to edit text in a font “you must have that font installed on your computer”. UPDF says it “keeps the same font only when that font is available on your system”, and Wondershare says that if the original font “is not supported in your system, you can’t edit the PDF text with it”. Readdle says a font can change while you edit when it “is not supported by the system and thus by our app”, and its fix on a Mac is to install the font in Font Book. Canva replaces a font it does not support “with a similar font”. Sejda asks you to pick a replacement when the font lacks characters you typed, and PDFgear’s guide says the original font is kept.

PDF Textfix works from the other end. It writes with the font inside the document, whether or not that font is installed on your Mac, and marks every character a fallback had to supply.

What does “keeps the font” actually mean?

A PDF does not store text the way a word processor does. Each line is drawn with glyphs, the shapes of the characters, taken from a font program. Most PDFs carry those font programs inside the file, and most carry only a subset: the glyphs the document uses and nothing else. A font name such as “ABCDEF+IBMPlexSans” in a file’s properties is the sign of an embedded subset font.

When an editor says it “keeps the font”, it can mean one of three things, and they are not equal:

  1. The same font program. The new text is drawn with the glyphs already embedded in the file. The letters match because they are the same shapes.
  2. The same family, from your computer. The editor finds a font of the same name installed on your Mac and draws the new text with it. If your copy is another version, widths and shapes can differ slightly.
  3. A similar font. The editor substitutes one that looks close. The edit is readable, but the line no longer matches the rest of the page.

Most of the vendor sentences in the table describe the second meaning, which is why they ask you to install the font. That works well when you have it. When the font came with someone else’s document, and is not one macOS installs, you may not have it.

The guide to why editing a PDF changes the font explains the mechanics in more depth, and the guide to PDF fonts covers embedding, subsets and missing fonts.

Why does a new letter cause trouble?

A subset only holds the characters the document used. Correct “Tuesday” to “Thursday” and every letter you need is probably there already. Add an accented letter, a currency sign or a digit the page never used, and the embedded font may not have it.

The demo cover letter in PDF Textfix’s screenshots is built to show exactly this. It is written without any accented letter, so its embedded IBM Plex Serif subsets lack “é”. Correcting the writer’s own name in its heading from “Renee Okafor” to “Renée Okafor” needs a character the document’s own font cannot draw. An editor has three honest choices here: draw it from another font and say so, ask you to choose, or refuse. Sejda’s online editor asks; the dialog says “The original font is missing some of the characters you typed.” PDF Textfix draws it from a fallback and marks it, as the screenshot above shows. The vendor pages read for the other editors do not say what they do in this case.

How does PDF Textfix choose the font for an edit?

It starts with the glyphs the document already has and goes outward only when it must:

You type é. The line’s own font has no é.

  1. Another copy of the same font in the file.
  2. The same font, installed on your Mac.
  3. The closest standard font.
Where a missing character comes from. When the line’s own font lacks a character you type, PDF Textfix looks in three places, in this order, and marks the character so you can see it.
  1. A glyph already in the same embedded font.
  2. Another copy of the same face elsewhere in the document; PDFs often embed one face as several subsets.
  3. The same font installed on your Mac.
  4. The closest standard font.

You see every step while you type. Characters taken from another copy of the line’s font are underlined. Characters drawn with a fallback font are orange, and the editor’s bar names the fallback font; its font line shows the line’s own font, such as “Font: Helvetica (embedded subset), 11 pt”. A character no font can draw is red; the bar says why and, when a close one exists, suggests a character, which Edit > Use Suggested Character (⌃⌘U) types for you. After an edit, the Issues pane lists the fallback fonts your edits used.

The fonts already in the file are never modified. Glyphs a fallback adds go into a new font object that only the inserted text uses, so the rest of the page keeps drawing from the original fonts as before. A font whose licence restricts editing keeps the characters the file already has, and the app never builds a new font from it; a missing character then comes from another face, or the edit is refused with the licence as the reason.

What PDF Textfix does not do is change fonts. It changes no fonts or sizes: the line keeps its font, size and position. The rest of the line stays where it is unless the new text would run into it. Then the app moves the rest of that line, says so in the bar, and Keep Following Text in Place puts it back. Shift Rest of Line (⌃⌘R) moves it by hand. For a different typeface you need a general editor, and the page on keeping the same font when you edit walks through the steps in PDF Textfix.

Which fonts can PDF Textfix write with?

The common embedded kinds. It edits text set in CID-keyed TrueType and CFF fonts with Identity-H encoding, and in simple TrueType fonts with their common encodings. It also edits the standard fonts and core TrueType fonts when a file uses them without embedding them. Simple CFF and Type 1 fonts reuse their own glyphs and take any missing character from a fallback font.

Some lines stay locked, and each one says why. A font “made of pictures”, a Type 3 font, cannot take new text. Neither can text in a Chinese, Japanese or Korean encoding the app cannot write, text that runs top to bottom, or text in a right-to-left or joined script.

Two cases change where a missing character may come from. In a PDF/A file, a missing character always ends up in an embedded font. The app never uses a fallback it would leave out of the file, so every font the document needs stays inside it. When a character comes from a font installed on your Mac, that font’s characters are written into the file, and the licence of a font you installed yourself is yours to respect.

How can you test an editor’s font claim yourself?

You do not need to take anyone’s word for it, ours included. This method works with any editor and any PDF you are allowed to edit:

  1. Pick a file whose fonts are not installed on your Mac. The guide to finding the fonts in a PDF shows how to list them; the free command-line tool pdffonts prints each font with columns that say whether it is embedded and whether it is a subset.
  2. Make two edits on a copy. One that only uses letters already on the line, such as swapping two digits of a date, and one that needs a new character, such as an accented letter the page does not use.
  3. Save as a new file and keep the original untouched.
  4. Open the saved copy in a second viewer and zoom to 400 percent on both edited lines. Compare the letter shapes, widths and spacing with the unedited text around them.
  5. List the saved copy’s fonts again. A new font name means the editor brought in another font, from your Mac or a fallback.
  6. Copy the edited line and paste it into a text editor. If the pasted text does not match what you typed, the text layer and the drawing disagree.

Two demo documents ship in the app, a letter and an invoice (Help > Open Sample PDF); they are synthetic, set in IBM Plex, which stock macOS does not install, and never count toward the free version. We have not published results of running this method across editors, so this page makes no claim that any editor’s output, ours included, is identical to the original. What PDF Textfix does check, on every edit before it applies it, is that every other character on the page stays where it was.

Which editor should you use?

If the fonts are installed on your Mac, or you are free to install them, the editors whose rule is “install the font” say they keep it in that case, and they do much more than change words. If you want to change the typeface on purpose, use one of them; PDF Textfix will not.

If the document came from someone else, its fonts are embedded and not installed, and you need to correct a word without the line changing typeface, an editor that writes with the embedded font is the tool for that job. PDF Textfix is free to try. Your first 5 line edits save clean. After that, saved files carry a watermark until you buy once. That is enough to run the test above on your own file before you decide.

Questions people ask

Why does my PDF editor change the font when I edit text?

When the font is embedded in the PDF but not installed on your computer, an editor that draws new text only with installed fonts has to use another one. Adobe, UPDF, Wondershare and Readdle each point to the installed font in their help.

Do I need the font installed to use PDF Textfix?

No. It writes with the font inside the document. An installed copy of the same font is used only when the file’s copies lack a character you type.

What does an orange letter mean in the editor?

That character was drawn with a fallback font, because the document’s own font does not contain it. An underlined character came from another copy of the same font, and a red one cannot be drawn by any font.

Can I change a line to a different font?

Not in PDF Textfix: it changes no fonts or sizes. For a different typeface, use a general PDF editor and check its font rule in the table above.