In PDF files both PostScript (type 1 and type 3) and TrueType fonts can be used. From PDF 1.6 onwards, OpenType fonts can also be directly stored in PDF files. Prior to PDF 1.6, OpenType fonts would be embedded as either PostScript type 1 or TrueType fonts.

By preference any fonts that are used in a layout are also included in the PDF file itself. This makes sure that the file can be viewed and printed as it was created by the designer. There are two mechanisms to include fonts in a PDF:

• Embedding - A full copy of the entire character set of a font is stored in the PDF.
• Subsetting - Only those characters that are actually used in the lay-out are stored in the PDF. If the “$” character doesn’t appear anywhere in the text, that character is not included in the font. This means that PDF files with subsetted fonts are smaller then PDF files with embedded fonts.

If certain fonts are missing from the PDF file, Adobe Acrobat and Adobe Reader will automatically try to emulate the missing font by using one of the Multiple Master fonts that are built into these programs. This way, the document will not be represented exactly as the designer wanted it to, but at least the text won’t reflow.

The Multiple Master fonts that are used for this are:

• Adobe Serif MM
• Adobe Sans MM

Which fonts are used in a PDF?

Adobe Acrobat and Adobe Reader offer a ‘Font info’ option in the “Document info” window. This option will not list all fonts used in the document. It will only show the fonts that are used on the active page. Do not rely on it to get an accurate overview of fonts used in a PDF document.

To get an overview of all fonts, you need a plug-in like Enfocus PitStop.

Embedding fonts

Acrobat Distiller offers an option to automatically add missing fonts to PostScript files it has to process. In the font locations menu, the user can define several folders that have to be searched for fonts that are missing in the PostScript file. Distiller only needs the printer fonts, it does not need the screen fonts.

Fonts that are not included in PDF files
Older versions of Adobe Acrobat (Acrobat 3.x and earlier) will never embed the following 14 fonts t in a PDF file:

• Courier, Courier-Bold, Courier-Oblique, Courier-BoldOblique
• Times-Roman , Times-Bold , Times-Italic, Times-BoldItalic
• Helvetica, Helvetica-Bold, Helvetica-Oblique, Helvetica-BoldOblique
• Symbol
• ZapfDingbats.

These fonts, excluding ZapfDingbats, are called the Base 13 fonts.

From Acrobat 4.x onwards, there is no problem embedding the above 14 fonts. Instead we got another restriction: if the licensing policy of a TrueType forbids the font to be included in a file, Distiller 4 and later will respect this restriction and will not embed the font.

Subsetting fonts

It is also possible to only include those characters of a font that are actually used in the publication. This technique is called font subsetting. Using the ‘Subset fonts below XX %’ parameter of Distiller, you can decide how many characters have to be used in a publication before a subset of the font is included.

There are 2 advantages to subsetting fonts

• It reduces the size of a PDF file and can be handy if file size is really crucial, for instance for PDF files that will be downloaded from the web.
• RIPs will always use a subsetted font, even if the full font is already available on the RIP. This way text reflows caused by differences between fonts can be avoided.

There are two disadvantages to subsetting fonts:

• If you want to edit text in Acrobat and the character you need is not included in the subset, it cannot be used in the correction.
• Merging two files that contain a different subset of the same font can lead to missing characters.

Outlining fonts

Sometimes it can be practical to convert all fonts within a PDF to outlines. This way the text in the PDF is ‘locked down’ and will not be output differently by a RIP because of some weird font behavior. You should be aware that converting fonts to outline affects their quality: at smaller type sizes the output quality will be slightly inferior (because font hinting is gone) and small type may also fatten up a little.

There is an option to outline all text in the Advanced > Print Production > Flattener Preview option in Acrobat 8 Professional. This will only outline text on pages that have transparency in them so the trick is to add a transparent object to each page (either using a watermark or using PitStop Professional). You can find a discussion and sample screen shots about this trick in this thread.

Recommendations

In order to minimize surprises with fonts in PDF, try following these guidelines:

• Always set Distiller to error out when a font is missing.
• Always embed all fonts.
• Always embed complete fonts, do not subset fonts. This avoids rare problems when for example putting several pages using the same font in different subsets onto the same plate.
• Always turn off “Use local fonts in Acrobat” on every machine in your shop.
• Always do a preflight for occurrences of Courier in PDF files you process or send away or receive (in case a font has been substituted)
• Never use the TouchUp text edit tool.
• Remove all fonts from your RIP (except Courier, Helvetica or any other font that your RIP may absolutely require to operate correctly).
• Use only Adobe PostScript 3 or Harlequin based RIPs or output devices. There are some RIPs/output devices around that have problems handling certain font stuff (e.g. CID fonts as in PDFs produced by InDesign).