How do I turn a Safari Webarchive file into a folder?

Solution 1:

WebArchiveExtractor

I recommend WebArchiveExtractor. You can drag .webarchive files to this app which will extract the file into its individual files in a folder.

You can customise the output in Preferences, including setting a custom index file name:

WebArchiveExtractor is open source on GitHub

As of June 2021, it does build perfectly in Xcode (from the link above) and works very well.

Solution 2:

Is there any currently available software that can convert a Safari webarchive file into a more standard format?

If you are comfortable with command line, there is a tool textutil on Mac OS for converting webarchive file to txt, html, rtf, rtfd, doc, docx, wordml, or odt.

Example:
textutil -convert html /Users/USERNAME/NAME.webarchive

For converting webarchive file to pdf, try "Wondershare PDF Editor for Mac". http://www.wondershare.com/pdf/how-to-convert-webarchive-to-pdf.html