Embedded fonts in PDFs: what it is and what it is for

1What is an embedded font?

A font is the file that contains the shape of every letter, number and symbol of a typeface. When you create a document with a specific font, your computer uses it to draw the text. But whoever receives the PDF may not have that font installed. Embedding it means saving inside the PDF itself the letter shapes it needs, so the document looks the same on any device, program or printer.

It is one of the reasons PDF is considered a reliable format for sharing: what you see when you create it is what the recipient will see, regardless of what they have installed.

2What happens when a font isn't embedded?

The viewer has to improvise. If the font doesn't travel with the file and isn't on the device either, it replaces it with a similar one. Sometimes the change is almost unnoticeable; other times the letter widths are different, the text overflows its boxes, tables fall out of alignment and line breaks change.

The worst case is symbols and languages with special alphabets: instead of the right letter you see empty boxes, question marks or meaningless characters. Accents and special letters can also fail if the substitute doesn't include those characters.

A real and frequent case is the trendy font in an invitation or a resume: it looks perfect on your computer, but when opened on another device it switches to a generic font. The fix is almost always to export again making sure fonts are embedded, rather than trying to repair the file you already sent.

3Subsets, types and exceptions

To avoid bloating the file, most programs embed a subset: only the characters that actually appear in the document. That way a font that weighs several hundred kilobytes adds only a small fraction to the PDF. The trade-off is that if you later try to edit the text with letters that weren't in the subset, the program may have no way to draw them.

There is also a group of basic fonts that PDF viewers usually know without needing them to be embedded, such as Helvetica, Times, Courier, Symbol and ZapfDingbats. The fonts actually in use can be TrueType, OpenType or Type 1, and each may or may not be embedded. Some fonts have licenses that limit embedding, something to keep in mind for commercial work.

• Subset: lighter file, limited editing.
• Full font: larger file, more freedom to edit.
• Basic fonts: may not be embedded.
• Font license: check whether it allows embedding.

4How to check and fix font problems

Most PDF viewers show the document's fonts in its properties, indicating whether each one is embedded or a subset. If you see a font with no embedded label, it is a candidate to fail on other devices.

To avoid problems, when exporting from a word processor choose the Save as PDF or PDF/A option instead of printing with a virtual printer using default settings, and include the fonts. If you receive a PDF with odd characters, ask for a re-exported version; if you only need the content, you can extract the text or use OCR on an image of the page.

5Common myths

One myth is that embedded fonts make the PDF much heavier. With subsets, the difference is usually small. Another is believing that any PDF lets you change the typeface freely: the text is as it is and, in many cases, editing means covering it up and typing it again.

People also think a scanned PDF has fonts. It doesn't: a scan is an image and contains no fonts; if OCR has been applied, the invisible text may have a substitute font, but what you see is still the image.

6Fonts and Rayo PDF GO

Rayo PDF GO does not include a panel to view or embed fonts, so if your goal is to prepare a file with strict typographic requirements, do it in the program where you created the document. You can work with your PDFs: Edit PDF to add text, Watermark or Page numbers to add elements, and Compress PDF to reduce the size.

If a document shows corrupted letters and you need to rescue the content, try Extract text, or PDF to images followed by OCR. Everything happens on your device without uploading the file.