The Upload Dialog and thumbnail area of the main view can act as Web Print Drop Zone. You can (multiple) select files in any desktop application and drag & drop them into the zone, after which they are immediately uploaded. When files are dragged into the zone, it lights up with a green border.
A Drag & Drop of an URL of a Web Page or Document has the same effect. In that case Web Page or Document is server-side downloaded and rendered as PDF. See Server-side Download properties.
The Drop Zone can be enabled at Section 4.11.6, “Web Print”.
For plain text files dropped in the Main Drop Zone, the selected font in the Upload Dialog is used.
Rendering a Web Page by a Drag & Drop of its URL gives best results when wkhtmltopdf is installed.