Replace wrong PDF non-latin characters

Hello,

I can use many operating systems, many applications, many programming languages.
But the best language for me is C# .NET. I can learn to use any application.
PDF files often are created with problem : non-latin characters are displayed but do not exist. Let's say : Ž is displayed correctly but then copied is shown incorrectly.
I open PDF file with 'Foxit Reader' Windows, 'Goodreader' iOS. You can copy text anywhere with copy-paste function.
I don't have original file(txt, word) from which PDF was created.
The problem is font : somebody created PDF with wrong font which does not accept non-latin characters. The problem started from wrong font in PDF.
Wrong font name : WtUStoneSerItcTMed7qREumM

Times New Roman accept non-latin characters but I cannot change font for whole PDF. I've tried to change it to Times New Roman for whole PDF page - disaster.
I can only change font for very exact letters with command 'Replace All' Ctrl+H.

I need to have correct non-latin characters so that I could search any word within every page of PDF :

All incorrect symbols :

I am able to fix these wrong letters with 'Foxit Advanced PDF Editor'. However, I am not able to fix these wrong characters with 'Foxit Advanced PDF Editor' then they are at the beginning of paragraph(wildcards are not working for whatever the reason is) :

But I am not able to fix these :
I need to replace incorrect symbols into correct symbols. What other PDF editor applications, systems, etc. do you suggest ?
Here's how I work with "Foxit advanced PDF Editor" :

Thanks