"A file name can not contain any of the following symbols … \" - What's up with that?
The "\" character is reserved for separating the names of directories (folders) from each other and from the filename.
For example If I have a folder
c:\foo containing a subdirectory
bar and I put a file named
bar I could refer to it as
c:\foo\bar\file.txt. If I were also allowed to put '\' in a filename, I could put into
c:\foo a file named
bar\file.txt and Windows would then have two different files in two different directories that could both be referred to by the same name
c:\foo\bar\file.txt. This would cause problems.
Other characters also have special meanings and so are not accepted as part of the file name.
According to Adobe Reader (File, Properties, Description, Title) the title of http://users.utu.fi/harju/graphtheory/graphtheory.pdf is "GraphTheory.dvi". I was able to cut that and paste it into a file name.
The first two lines of the text in the PDF are "Lecture Notes on", "GRAPH THEORY". I cut those out and pasted them into a file name - this resulted in a file name of "Lecture notes on". I didn't get the error message you refer to.
If I cut out all the text on the first page, this includes "email:" and ":" is one of those characters that is not allowed in file names (in Windows filesystems)