You can get PDFs corresponding to single pages of the yEd Manual that is online available: http://yed.yworks.com/support/manual/index.html (see the button in the upper right corner of each page).
Printing the help pages that come with yEd can be done like so:
Open the help window.
Expand the entire navigation tree.
Select all the page titles in it.
Click on the printer button.
(But note that the resulting document will have quite some pages...)