I have a test instance of Plone 5 and when adding files, like pdf, they end up as plain text, not application/pdf. I see in the documentation that this is controlled in zope.filerepresentation. The docs refer to this:
In Dexterity, the PUT() method is overridden to adapt self to
zope.filerepresentation.IRawWriteFile, and call its write() method one
or more times, writing the contents of the request body, before calling
close(). The mimeType and encoding properties will also be set
based on the value of the Content-Type header, if available.
I am using cadaver 0.23.3. When adding file to my existing plone 3.3.5 site, the files are treated correctly out of the box. I would like to duplicate that in current Plone.