What you're looking for is, depending on whether your Ebook is extracted from 'Pure Text' to the Flash Player or from a 'Series of Images', really hard or 'trying to lick your elbow' hard.
First of all, there is no tool out there that will do some 'EXE To PDF' conversion for you in some kind of 'EZ 1-2-3' interface (or any kind of interface). Period.
Trying to extract the data from Flash Player using a Debugger will yield no results, since Flash Debuggers are meant to work with '.SWF' extension files or the like, not with '.EXE'.
Using a Hex Editor to try to extract the block of code that corresponds to the Unicode or Ascii text portion of the EBook with the hope of using some online 'Hex to X' converter is possible, while you would be in for a challenge. But, as I said in the beggining: there is just a small chance of this happening and only if there is 'text' and not 'images' inside that 'EXE'.
Anyway, probably the best you can do is follow Bengi's comment and take a series of screenshots of the book and copy them to a Word file from where you can create the PDF. If the book is too long, you can create a Macro that will do this for you.