>This was the original of my file. Original File.txt file format is '.fdf' 'PDF Comment File'
Care must be taken to ensure that the file being read is in fact a text file. That is, it does not contain binary data that may be misinterpreted if read and processed as part of a text file. The contents of the sample files you provided appear to suggest that these are not simple text files. If that is the case, then they probably should be read and processed as binary files. For example, using ReadAllBytes rather than ReadAllText:
File.ReadAllBytes(String) Method
https://learn.microsoft.com/en-us/dotnet/api/system.io.file.readallbytes?view=net-7.0
Generally the text processing file routines are not reliable when unexpected binary characters are encountered.
File and Stream I/O
https://learn.microsoft.com/en-us/dotnet/standard/io/
"TextReader and TextWriter - serve as the abstract base classes for other readers and writers that read and write characters and strings, but not binary data."
- Wayne