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A
Anymouse5FCE
Participant
May 14, 2021
Question

Font for visual indication of digital signature

  • May 14, 2021
  • 1 reply
  • 7080 views

Hi, I use LaTeX to create PDF documents and Acrobat Reader DC to add a cryptographic signature for authenticity.

 

When Acrobat Reader DC signs the PDF file, it gives a nice visual indication that the document has a cryptographic signature but there are two issues:

 

A) It uses the Helvetica font but does not embed the subset needed---which can vary because of the timestamp showing when it was signed.

B) Part of my name is long enough that it overflows to a second line, breaking the single word into two. I tried making the form box wider but it seems that just triggers Acrobat Reader DC to use a slightly bigger font size with same result.

 

Is there a way to tell Acrobat Reader DC to use Helvetica Narrow instead of Helvetica? Both are part of the "Base35" fonts.

 

And is there a way to get Acrobat Reader DC to embed the subset that it uses? Some places where I upload a PDF will not allow me to upload if not all of the fonts are embedded, even Base35 fonts.

 

There are programs to add missing fonts but it stands to reason that would then break the cryptographic signature, no?

This topic has been closed for replies.

1 reply

T
Test Screen Name
Legend
May 14, 2021

"Is there a way to tell Acrobat Reader DC to use Helvetica Narrow instead of Helvetica? Both are part of the "Base35" fonts."

 

Base35 is a concept in PostScript, not PDF. PDF has a "base14" font list instead. This includes Helvetica but not Helvetica Narrow. The magic fonts, in PDF, are designed to work everywhere whether or not Helvetica is installed; suitable substitution taking place if necessary.

 

(I don't know anything about font options in this specific use cases, sorry).

A
Anymouse5FCEAuthor
Participant
May 14, 2021

Thank you for the clarification on the Base35 for Postscript vs Base14 for PDF. That probably means using Helvetica Narrow is out unless the entire font is embedded, I seem to recall to switch fonts in a non-signature form field that the entire font has to be embedded if not one of the "core" fonts and I assume that applies to signature form fields as well.

 

My crypto keypair identity is "The Anymouse Prophet" and what happens is the "e" on "Anymouse" gets floated to the next line because Adobe's visual indication of a signature is two boxes side by side, and making the entire field larger just results in Adobe Reader DC using a larger font size with same problem.

 

Helvetica Narrow might fix that but if it's not in Base14 I doubt there's any way to tell Adobe Reader DC to use it w/o entire font being embedded first.

 

Still wish (hoping) there is a way to get Adobe to embed the subset it does use for the visual indication of signature simply because Base14 or not, some places require *all* fonts embedded.

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