Adobe fonts loading as squares

[AM2023-4]

I am having some issues with Adobe Acrobat Pro (64-bit), I know that it is something to do with the font as half of the text is legible and then the rest is just a series of squares. I have tried to restore previous versions of the PDF but there are no previous versions stored on my computer. I have looked up the problem and it mentions embedding fonts and half of my fonts are embedded and the others aren't. I have tried exporting to word and then back to PDF but it still isn't working. I have been into properties and attempted to get the software to embed all fonts but it still isn't helping. Also when I manually try to change the font the following error appears: "Some of the characters are not available in the font you selected. Try choosing a different font". The font causing an issue is Arial but the thing is, I don't know why only sections are behaving this way.

I have spent around 2 days trying to sort this out and even if I convert the PDF into a plain text file, those squares are presenting as a series of dots. 

[Abambo]

This happens, when the font you are using does not have the correct characters. You need to try to find the font that has the corresponding character in their definition. Just out of the gut, I would try an Asian font set, like Source Han Sans CJK Simplified https://fonts.adobe.com/fonts/source-han-sans-cjk-simplified-chinese.

Please let me know if that solves the problem.

[AM2023-4]

Hi Abambo,

Thank you for your response. I have downloaded the font family you recommended, but when I change the font from Arial to Source Hans CJK simplified Chinese, unfortunately it is still coming up with the same error "Some of the characters are not available in the font you selected. Try choosing a different font". To be honest, I think this document is just not going to revert back to the original, which is hard for me to digest but I think I have spent more time fixing this than entering the data. Please do let me know whether there are any other solutions though, as I am in too deep now to not resolve it! Here is what happened when I tried to change the font, save the document and re-open it. 

[Abambo]

How did this document getting created? Check the properties? 

What is the source of the document? What does properties say about the fonts? 

It's getting a fishing operation without access to the original file.