On a Unix system, all lines end with just a linefeed. On a Macintosh, all lines end with just a carriage return. This is a sad fact of life.
Canonical text has a carriage return and a linefeed at the end of each line of text.
This makes it easy to share text files across different systems. But encrypted text cannot be automatically converted by a communication protocol, because the plaintext is hidden by encipherment. At the receiving end, the decrypted plaintext is automatically converted back to whatever text form is appropriate for the local environment. This mode is automatically turned off if PGP detects that the plaintext file contains what it thinks is non-text binary data. That's what I do.