Hi Sawan -
As you said, there are too many variables in play to allow someone to give you a semi-realistic number to work with. However, the amount of time your report takes to render in Tableau Desktop is a good place to start. Generally, a report will never render any faster on Server than it does in Desktop. So, you could get a rough guestimate my establishing the report rendering time in Desktop, multiply it by 100K and then add additional time for "server overhead".
Again, this is only going to give you a very, very rough idea.
Okay, fair enough.
Do any of the current Tableau customers use Tableau to generate batch reports in PDF format? For like 100k to 1m ?
Does Tableau populate PDF directly or converts HTML to PDF?
Does the report goes as an image in PDF?
Is it advisable to use external PDF generator? Do you have any comparison on that?
Any other profiling on Tableau?
I do know of some customers who do this, but I don't really know how many reports they are trying to generate at a time. Maybe a user on the forum can tell you their experiences on that subject.
I personally don't know the internals of how we generate PDF reports - a few of the Developers are active on this forum and perhaps one of them will jump in. On the subject of 3rd party generators - I'd think that leveraging one of these would only slow things down for you.