Yes. What's the alternative?

You can use non-ASCII characters in your Perl source as long as you know what encoding the file is in, and you tell Perl. My suggestion would be to save the file as UTF-8 and add use utf8;.

The editor (Komodo) doesn't ask me when saving.

A quick Google search offers the following solution to change the encoding of a file: "right click the file in the left pane, select property, In the File Preferences, find File Settings section, and you see the Encoding selection menu." (https://community.activestate.com/node/10558)

You mean I need to replace all Umlauts by hex escapes?

No, that was meant as a test: If you use hex escapes, and your problems go away, then you know the issue was the encoding of the Perl source file. If they don't go away, the source is likely PDF::API2, or, if you're getting your text from a source outside of the Perl source, that source.