For information about how fonts work and how they affect your documents see the Understanding Fonts PDF here.
If texts or page numbers are missing (or the font is simply incorrect) in PDFs check to ensure that all users have the correct fonts installed. If a user is missing a font this font will be replaced by InCopy/InDesign which may differ in size and use a different measurement for kerning. This may cause the font to be too large for a text frame created for the specific font intended. In which case the text will not appear. If you are missing fonts see the page found here.
You can see which user has created a PDF by selecting the chapter, clicking on the "Chapter" menu and then selecting "Show earlier versions". This will determine which particular user is missing the fonts required.
For more information about how PDFs work when using CtrlPrint see the information here.