Use an online editor like Smallpdf to click on the affected text blocks and manually change the font from the "CIDFont+F1" dropdown to a standard font like Arial.
If you have access to the original Word or InDesign file, re-save it as a PDF and ensure the "Embed all fonts" option is checked in the settings. Impossible fonts to be found / Fontes impossíveis de achar cid font f1 f2 f3 f4 f5 f6 f7 fonts free download work
Because these are generic names, "F1" in one document might be a different font than "F1" in another. However, many users have found success replacing these missing fonts with standard system fonts that share the same appearance: Use an online editor like Smallpdf to click