This PHP Script has an Anti-Leech feature turned on.

Make sure you are accessing this file directly from www.steam-brite.com

It seems you are trying to get it from https://steam-brite.com/literature/schematics/index.php?dir=Pullman+Holt%2F&file=GB1090FPARTS.PDF

Your IP address has been logged.
3.135.194.138 (ec2-3-135-194-138.us-east-2.compute.amazonaws.com)

Here is a link to the directory index the file is in:
http://www.steam-brite.com/literature/schematics/index.php?dir=Pullman%20Holt/