PDF Symbols Disappear when Editing in Acrobat Pro

This can be due to diffrences in encoding between the version of Calibri used by the author/program when the PDF was created, and the version YOU have when you are doing edits. As soon as you try to edit with your version, all of the special symbols are no longer valid for that encoding and will change to something else, gibberish, or nothing at all.

(If you opened one of the existing PDFs in Illustrator, you can see what hell an encoding mismatch can cause).

Often we need to edit the pdf directly in Acrobat (usually only the header/footer). Sometimes when I do this  these symbols dissapear (≥  ≤  >  < ).

By @Kasi5C4F

Sometimes when you edit PDFs in Acrobat, rather than in the source program like InDesign or Word, you'll lose characters. They can disappear randomly and on random pages.

Some things that can cause this:
 

1.  The PDF is tagged. Tagged PDFs can't be edited at all. They loose their content.
    
2. The font wasn't embedded into the PDF at the time it was exported from its source document. Make sure this option is checked in your export options.
    
3. The font can't be embedded into the PDF because it has restrictions on its use. Check the font's properties and ensure it has "embeddable" or "editing embedable" in its description.
    
4. Those glyphs aren't available on the font you've chosen. Calibri doesn't have a wide range of STEM characters and doesn't have any of the folowing glyphs.
   Less than / Greater than symbols in Unicode: U+2264 and U+2265.
   Preceeds / Succeeds symbols: U+227A  and U+227B (they look similar to the tradition <> symbols, but are different).
   Wikipedia has an excellent webpage on math symbols https://en.wikipedia.org/wiki/Mathematical_operators_and_symbols_in_Unicode

Try using a better font with more math symbols, such as Noto Sans Math at https://fonts.google.com/?query=noto  or Arial Unicide MS (an advanced form of Arial that shipps with some Windows programs).

Hi Kasi,

I've heard of things like this happening but in that case it was the "n" dash ("–"). There is a bug somewhere between the font, InDesign, and Acrobat. Last I heard everyone was busy pointing fingers.

One temporary solution might be to just substitute a different font that's "close enough."

I've been using computers long enough that sometimes it's better to get the job done than trying to get the job done the way it's supposed to work!

Please update on what font was being used and if an alternate font works what that font is. 

Thanks!