Changing one character in a PDF

I saw a post on X saying Changing a hyphen to an en-dash increases your PDF file size by ~10 bytes. My first thought was that it had something to do with hyphen being an ASCII character and an en-dash not. Changing a hyphen to an en-dash would make a UTF-8 encoded text file a couple bytes longer. (See why here.) Maybe adding one non-ASCII character could cause the file to include a glyph it didn’t before. I did a couple experiments. I made a minimal LaTeX file with only the text See pages 9-10. and another with See pages 9--10. (In LaTeX, a hyphen compiles to a hyphen and two hyphens compile to an en-dash.) I compiled both files using pdflatex. The PDF with the hyphen was 13172 bytes and the one with the en-dash was 13099 bytes. Replacing the hyphen with the en-dash made the file 73 bytes smaller. I repeated the experiment with a Libre Office ODT document. Changing the hyphen to an en-dash reduced the file size from 13548 bytes to 13514 bytes. Then I went back to LaTeX and pasted a…