Can I find a PDF manual for Premiere Elements 2020 and Photshop Elements 2020 somewhere?
Adobe seems to have drifted away from printed manuals and moved to online help. The most recent .pdf manuals are dated in 2018 and probably missing some of the newest features.
I agree with griffintkm. I don't think there are any other books on Premiere Elements. There may be more on Photoshop Elements.
Take a look at Steve Grisetti's books. The Muvipix.com Guides to Premiere & Photoshop Elements 2020. Much better than the PDF's and they are current.