Thanks for your reply.
I'm using the latest version of Acrobat (19.012.20040).
I open the file in Acrobat, then click on "Edit PDF" from the right pane, and then "Edit" icon (which is described as "Edit text and images").
Answering yout last question - there are some third-part applications (not Adobe) for PDF files to view details like glyphs, fonts, images and other parameters of every file. I don't want to advertise this or that application.