The big question is in which character set you do see the trademark sign, or, which ISO-8859-1 character are you seeing as a SUB character (whatever that is?)
In ASCII there is a control character SUB (ctrl-Z) which has the character code 26 decimal (octal 032, hex 0x1A) -- is that what you have in your file? What would be a useful encoding to transfer it to? The following will translate all occurrences of this character code into the Unicode trade mark symbol character U+2122 in the UTF-8 encoding:
Code:
perl -pe 's/\x1A/\xE2\x84\xA2/g' file.orig > file.utf8
Or in ISO-8859-1, there is the Registered sign ® at code point 0xAE, would that be a useful substitute?
Code:
perl -pe 's/\x1A/\xAE/g' file.orig > file.iso-8859-1
This assumes that the SUB character really is character code 0x1A; if it's not, but you can find out what it is instead, it should be trivial to adapt either of these one-liners to something which works for you. Some Windows code pages have the trademark symbol at 0x99 so that might be a thing to try if 0x1A doesn't work for you (but again, if you can look at the raw bytes in the file, you don't have to guess).
