Warning

Glyphs & Ligatures

Redlin have been supplied press ready PDF (Portable Document Format) files from at least four independent sources. All the supplied pdfs were generated from Indesign using the export facility. With all files we have experienced some degree of problems with glyphs & ligatures at output stage.

What are glyphs & ligatures?

Glyphs – A visual representation of a ʻletterʼ, ʻcharacterʼ or ʻsymbolʼ in a specific
typeface/font.
Ligature – The joining of 2 or more characters to produce a single glyph.
Most common ligatures fi ffi ff fl ffl

After extensive investigation we have discovered that Acrobat 8 does not support Ligatures and will display blanks in their place eg. ʻflexibleʼ becomes ʻ exibleʼ. When creating the PDF file no warning is produced that this has occurred. It is believed that earlier versions
of Acrobat, version 7 and below do not experience this problem.

The problem so far has only manifest itself with indesign. It would appear to be a combination/conflict between the export setting used, the fonts and the transparency filters within the source document.

What can be done?

1. Convert all type to outlines.

Prior to exporting file to pdf, convert all the fonts to outline, negating the potential problem. The type is now a vectorized image which is not effected by glyphs and ligatures. The drawback to this is – it is advised to keep a copy of the file without converting type to outlines in case of any alterations that maybe required. Once converted these changes cannot be easily made.

2. Export the file on an alternative setting.
When exporting the file select:
Standard: PDF/X 1a-2001
Compatability: Acrobat 4 version 1:3

The important thing here appears to be the compatability details. Any setting higher than Acrobat 4 Version 1.3 does not allow the facility to flatten at pdf creation stage. It is this relationship with Acrobat 8, the transparency and fonts that cause the ligature problem at
outputting stage.
Correct: This setting enables you to flatten transparency at pdf creation stage.

Setting to avoid when exporting the file: Standard: PDF/X 1a-2001 or above Compatability: Acrobat 5 version 1:4 or above

Incorrect: This setting maintains transparency at pdf creation stage. Leading to potential problems.

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