Bottom line up front: after looking into it, it seems there are 3 options to get both the printed rule book and the PDF.
1. Purchase from Free League directly. Price (approx): 44 Euro / $48. Seems the least expensive.
2. Purchase the printed book from a local store that participates in Bits and Mortar, get the PDF through the Bits and Mortar program. Price: Whatever the store price is (mine was 50 Euro) plus the cost of the PDF, if there is a cost. I don't know details about who provides the PDF or what the price is. I just learned about this program reading this thread and there is no information on the PDF price or provider from the Bits and Mortar website. Although it does list the ALIEN Rule Book PDF as being available through the program.
3. Purchase the printed book from a local store (that DOES not participates in Bits and Mortar), purchase the PDF at drivethrurpg.com separately. Price: Whatever the store price is (again, mine was 50 Euro) plus the PDF price of $25 = about 72 Euro or $80. Seems to be the most expensive option.
I purchased my book at my local game store and emailed the service desk at Free League to ask about this topic. I explained that I bought it locally, that the store from which I bought it does not participate in Bits and Mortar, and asked if there was an option to purchase a PDF version of the rule book directly from Free League at a price that is lower than the price at drivethrurpg.com. The reply I received from Free League in its entirety was this:
"You can buy all of our pdfs for a reasonable price at Drivethrurpg.com."
I disagree that this is a reasonable price. I purchased the book for 50 Euro at my local store. Purchasing the PDF at drivethrurpg.com costs an additional $25. To buy the book locally and to pay for the pdf from drivethrurpg is approximately 72 Euro / $80 in total. For 44.09 Euro / $48.43 at the Free League store, one can get the book and the PDF. However there is no option to buy the PDF separately from Free League that I can see.
The pricing and the lack of a PDF purchase option from Free League don't make sense to me. Especially considering the Free League's membership in a program to promote purchases at local game stores (ie Bits and Mortar). If the store is not a member of Bits and Mortar, then the current setup discourages one from from purchasing the book from local game stores.
Why not purchase from a Bits and Mortar store? I purchased the book in a major European metropolis / capital city. According to the Bits and Mortar website, there is one participating Bits and Mortar store in the whole city. I asked that particular store if it had the book and it did not. In fact I had to ask at three or four different game stores in the city before I found one with the book available to purchase.
I hope others find this information helpful.