Is it normal for PDF files to open in Draw? Some of the parts are gibberish
It’s normal to be able to open PDF-files in Draw for editing, but for normal viewing it’s better to use a dedicated PDF-reader; there are tonnes of these.
Draw can handle most of the features used in standard PDF’s, but is lacking some of the exotic and under-documented ones.
If the problem is that PDF’s open by default in Draw, and you want them rather to be opened in some other application, then you have to change the file association (often you can right-click on a PDF in a file-manager, choose “Open with…”, choose application and tick “Always use this application for this kind of file”).