Section 508 Accessibility Error - Calibri ligatures not processing to Adobe Acrobat

[PowerTrain]

Something changed recently in Adobe Acrobat. We witnessed an error with ligatures in a font. The program actually tags the information incorrectly and if you use the reader, it reads the mixed up text.

Calibri ligatures not processing to Adobe Acrobat. This is a recent error.

[Abambo]

How do you create the Acrobat file?

I see, you used the Acrobat tools to create the file. This looks like a general Acrobat problem with ligatures. https://acrobat.uservoice.com/forums/590923-acrobat-for-windows-and-mac/suggestions/31943371-adobe-a...

[Bevi Chagnon - PubCom.com]

The root of the problem is Unicode itself: it does not have dedicated codepoints for tt and ti ligatures.

The standardized Unicode ligatures for English/Latin are:

U+FB00	ff	Latin Small Ligature ff
U+FB01	fi	Latin Small Ligature fi
U+FB02	fl	Latin Small Ligature fl
U+FB03	ffi	Latin Small Ligature ffi
U+FB04	ffl	Latin Small Ligature ffl
U+FB05	ſt	Latin Small Ligature Long S T
U+FB06	st	Latin Small Ligature St

The missing tt and ti ligatures seem to appear with Calibri, which appears to be the only font I've come across that has its own custom ligatures for these 2 combos. They are not standard with the UNICODE set of codepoints.

See this related discussion at StackOverflow https://stackoverflow.com/questions/20193102/prevent-localreport-render-using-calibri-font-ligatures

If you'd like to use the tt and ti ligatures, you'll have to petition the Unicode.org consortium to assign them codepoints. Otherwise, forgetabboutthem.