Best way to display PDF in drupal as a slideshow
Drupal is essentially a framework, it can't do anything that a 'normal' website can't do. This includes displaying PDF files in the format you want.

The only way is to use Flash (as suggested on the SO post you linked to). This would involve either building the SWF file yourself using Adobe's tools, or using one of the dozens of tools available to build a navigable SWF from a PDF file (e.g. SWFTools).

Drupal only comes into the equation when you actually want to display the Flash file.

Some purists might actually argue that this is a bad idea anyway; you should probably allow your users to read PDF files using the software that they have chosen for that particular job. 

If you were trying to DRM your PDF for whatever reason then it might make sense, but as you're providing a download link to the direct file anyway I don't think this applies.