Text positioning in PDF – any compliant PDF viewer – is 100% deterministic.   
All of the algorithms for text (or any graphics for that matter) placement are 
described by the standard – ISO 32000.

That said, a big part of the algorithms for text placement is based on font 
metrics.  If the fonts are embedded in the PDF – then there is no question 
about what the metrics are and they will be consistant between implementations 
and platforms.  However, should the font not be embedded in the PDF, then a 
viewer is free to substitute any font that it wishes – in which case, the 
metrics (and glyph shapes, etc.) will vary.

Why, John, what are you concerns?   And have you reviewed ISO 32000 for the 
information about the PDF standard itself?

Leonard

From: poppler <[email protected]> on behalf of John Curci 
<[email protected]>
Date: Monday, September 23, 2019 at 12:23 PM
To: "[email protected]" <[email protected]>
Subject: [poppler] Poppler – Assumptions?

Is text positioning from Poppler "perfect"? Is the positioning of text a 
deterministic
result of the PDF format, or does Poppler make certain assumptions and guesses? 
What are some assumptions made?
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