Unfortunately, as you have discovered, there is currently a problem with the installation of svBuilder-Pro whereby Adobe AIR reports that the installation file is damaged.
This is not strictly true (the file is not actually damaged) and I suspect that the true nature of the problem is either a certificate problem or an issue with the application trying to verify the publisher.
However, due to the demise of Flash, SimpleViewer has been retired (since July 2017) and there will be no more updates.
We now focus our attention on Juicebox (our HTML 5 image viewer) and Showkase.
It is unfortunate that SimpleViewer is no longer being actively being developed but web technologies move on and Flash has served us well as a gallery platform over the years.
Please see this blog entry entitled "The End of Flash and What this Means for SimpleViewer." for details.
Due to the problems current facing SimpleViewer and Flash in general (please see this forum post for details), I would not recommend creating SimpleViewer galleries and would suggest that you use Juicebox instead.
The ability to create new SimpleViewer galleries was removed from Showkase v1.7.1 (released on 15 September 2017) and SimpleViewer-Pro is included in the Showkase Pro Viewer Bundle more as a courtesy for users of older versions of Showkase with pre-existing SimpleViewer galleries than anything else (although I'd still recommend converting SimpleViewer galleries to Juicebox galleries within Showkase by editing a SimpleViewer gallery page, going to the 'Advanced' tab and changing the page type there).
Although, as I mentioned above, there is no way to install svBuilder-Pro, you can still build a SimpleViewer-Pro gallery (if you really want to) by using the Adobe Photoshop Plugin or manually.
I hope this helps to clarify things.