The first point is that freely available does not mean freely
usable, not even freely redistributable. Many copyrighted works are
freely available, even placed under a Creative common licence, but
still have legal restriction on their uses, regarding for example
modification or commercial use. The fact that it is, or is not
available in print or some other form is irrelevant. The only thing
that matters is what the licence says. If you have no licence, then
every use is forbidden, unless explicitly permitted by local law,
though you are obviously permitted to read the document, as there
would be no point in making it available otherwise.
However, the copyright law of some countries (France for example)
allow private copying, provided it is for your own use (which implies
that you do it yourself). There may be a further restriction that it
is legal only if your access to the source work is itself legal, thus
preventing copies from pirated sources.
In your case, you have legal access to the document as it is freely
available. Hence, where law permits, you can make private copies on
whatever medium, including paper. However, using an online service to
get it printed would probably not be considered as doing it yourself.
Even going to a print-on-demand shop in the street might be legally
disputable.
Then, things seldom get that formal, and it is likely that no one,
author included, will object, especially if the book is not available
for sale in the form you seek, so that you cannot possibly cause him
any damage.
Further legal details (to add accuracy to previous answers)
If you are in a country that is a member of the Bern Convention - which
is most countries, USA included - the work is protected by copyright
regardless of where it was created, and at least as well as work
created within the country. Actually, in the USA, copyright protection
is higher for unregistered foreign works than for unregistered US
works.
In the USA, your legal risk in printing for your own use a book that
has not been registered with the Copyright Office is very low, since
the copyright owner cannot sue for attorney fees or punitive damage,
but only to get the price of the printed book.
But I am not a lawyer.