Feedly Pro offers a backup-as-PDF-to-Dropbox feature. Saves nice clean pdfs to dropbox. When I still used Feedly, I just indexed that folder.
Nowadays I’m just doing all of Feedly, Pocket, and IFTTT in DT3 using the features it provides. DT3 doesn’t currently create nice PDFs from news articles, but that’s due to a bug or something and should improve in 3.0.1.
I use https://www.printfriendly.com when trying to save PDFs of web pages without all the cruft. It usually does a great job of keeping just what you want, but you can also remove additional items if you want just by clicking on them.
I would seriously consider the Feedly “backup” option. Every article tagged with whatever you’d like could be auto-imported into DT as a PDF, so long as you’re using Dropbox.
Keep It generates a clean PDF of a webpage on both Mac and iOS and it wasn’t broken by the recent Safari update. It works better than the DEVONthink clipper (at least for the sites I archive from).