When using:

webPage = new QWebPage();

QPrinter printer;
printer.setOutputFileName(outputFilename);

webPage->mainFrame()->print(&printer);

I expected to see a PDF document with a valid text layer.

Got instead:
The text in the PDF wasn't searchable and if I tried to copy some text of the document into a text editor only unprintable characters were pasted. Selecting text in the PDF document worked, though.

This is also happening with the textedit demo, the text is not searchable.