Clicking the link to the PDF-manual gives an error. Ther is not one single .pdf-file in the folder where the link points to. See the screenshot by the following URL. Misleading as it is (and was) there is no real damage done.
I found the (2001!) PDF-manual version and put it where MGED looks for it.
Case closed! Sorry for disturbing.
This issue has been resolved in the latest (unreleased) version of the source code. Thank you for bringing the issue to our attention! You're welcome and encouraged to test and make sure this issue is resolved after the next source release of BRL-CAD.
The date is not really important. That introduction to MGED just covers the basic fundamentals, which have not changed much in 20 years. The Windows install not including the PDF is a known issue, however, and was fixed in a later release.