Assuming the filename is not overtly incorrect, when using strings
containing backslashes (the windows path separator) as you are doing,
you should use “raw strings”, preceeding the string with an r:
.set_input_files(r"C:\abc\update\abc.pdf")
Nonraw strings interpret various backslash escapes to indicate
particular characters, for example \n is a newline character.
The one which juumps out at me in your code is \a, which is the ASCII
BEL, code 7, which rings the terminal’s bell if printed to a terminal.
As such, your filename above has BEL characters where you expected the
two characters \a. Using a raw string avoids these escapes.
The other alternative is to use /, the forward slash, as the path
separator. As I understand it, this is also accepted in most Windows
uses:
.set_input_files(r"C:/abc/update/abc.pdf")
Note that regular strings ("abc") and raw strings (r"abc") both just
result in a plain old Python str string object. They are just
different notations for expressing a string value in Python code.