The PDF format has been around for at least 20 years now, and throughout that time it’s continued to add the latest and greatest technologies – from Unicode to OpenType – to its portfolio. This means that the range of fonts now supported are as follows:
Most of the fonts we see inside PDF files are OpenType, TrueType, Type 1 or Type 1C. MMType1, Type0 and CID fonts are all extensions of those formats, which leaves Type 3 as the black sheep of the flock.
Type 3 fonts, along with Type 1 fonts, were first released in 1984 along with the PostScript specification. Type 1 offered a condensed set of PostScript operators, along with special commands for hinting, which gives the renderer some ideas of which features are most important for readability. Type 3, in contrast, offered the full range of PostScript commands but had no commands for hinting. Upon launch, Adobe released full documentation for Type 3 fonts, but kept Type 1 to themselves – they didn’t release any documentation, and used plenty of encryption on their Type 1 fonts.
This set the font world on an interesting course. Font foundries favoured Type 1 but were forced to use Type 3, Microsoft purchased a reverse engineered PostScript interpreter with Type 1 support called TrueImage, and Apple started work on a competing font format.
They later traded access to this format – TrueType – with Microsoft in exchange for a license to use TrueImage. Apple then almost immediately replaced TrueImage with an official PostScript license from Adobe, but both companies started to work on building TrueType support into their upcoming operating systems. (Both Mac OS System 7 and Windows 3.1 would feature TrueType support upon their release in 1991 and 1992 respectively.)
Adobe’s response to the looming emergence of a rival format and their loosening control over Type 1 technology was obvious – in 1990, they released the Type 1 specification to the font foundries and Type 1 quickly overtook Type 3 as the format of choice. To this day Type 1 and TrueType technology remain popular, although admittedly primarily through OpenType, which combines features from both.
When Adobe debuted the PDF format in 1993, they included support for Type 1 fonts, and a new version of Type 3 which uses PDF graphics commands instead of postscript operators.
Though it has advanced features similar to the original postscript version, like full colour, bitmaps and shadings, I have only ever come across a handful of Type 3 fonts. Not a single one of them used any features which can’t be matched by Type 1 fonts. In addition to this, the PDF specification lets you use text as a clip for other drawing, so any features within Type 3 fonts could be emulated within PDF files.
Realistically, I don’t expect Type 3 fonts will ever disappear from the specification – Adobe has been known to remove features from the specification, but it certainly isn’t a common occurrence. Plus it’s included in the archival format PDF/A, so it could be around for decades to come… I still can’t help but wonder if Type 3 adds anything, though – and if it does, I’m yet to see it.
Do you disagree? Have you used Type 3 fonts in any of your documents? Let us know in the comments!
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