Pasting every x characters

I'm not really sure if this should go here or in coding (since I'm mostly working with Visual Studio). Anyway, I'm working on a project that requires me to take a file and insert the same thing every 8 characters (or after every 8 bytes).

The file is pretty long and having to paste it in every 8 bytes will take forever, so I was wondering if there was a program that could insert something after every specified number of characters to make things a lot quicker. Better yet, is there a faster way to do it directly in Visual Studio?

Thanks.

 

If you can code, code a simple text manipulation program to insert those characters from a file into another file.