Read webpage offline

I find a web page I want to store in DTPO, for off-line reading.

Alas, whatever format I choose - Rich Text, Web Archive, HTML, PDF - does not make the entire page available off-line. If I’m online, they open up beautifully. But not off-line. Am I doing something wrong?

At least plain/rich text, formatted notes and PDF documents should always work but both HTML and web archives (due to the limitations of this format and the dynamic nature of modern websites) might not work as expected.