> even though obviously these days a doc-type declaration is important.
Not in PD4ML scenario. By a PDF generation the browser expects to receive PDF bytes only. If the response is leaded by the XML declaration, first: the data is misleading, as it is not “xhtml-strict” in fact; second: the declaration bytes break all object offsets in the document. Acroread can recover it on-a-fly, but it is not safe and by slow systems a pop-up with “rebuilding xref table” (or something like that) may appear.
PD4ML itself simply ignores the declaration.
The enable=”false” issue is in our TODO list for the next beta.