You would instead revisit the requirement. In PDF, a digital signature is always effective for the whole document, whatever page it marks. We often hear of this sort of requirement, but it comes from a flawed conversion of paper workflows.
One would think that software would meet a client need, not the other way around.
Additionally, it is not a flowed workflow. Think about legal documents for change orders etc... each page (say of a design) might need approval, because each page has different content (designs) that need approval. A client can't sign off on the entire package, but needs to approve individual elements within the larger document.
The design might be flawed, but if it is, it is the design of PDF digital signatures that is the problem.
I don't know how this kind of job is usually managed, but it isn't by digitally signing 100 times. Given that the signatures are per-document how would you establish which pages the client is approving? I can see the problem; maybe PDF isn't the solution.
If you did manage to sign 100 times, the way signatures are done is that each is a wrapper on the PDF to that time. Opening the PDF would require doing signature validation and unwrapping 100 times over; could take hours to open, or so it seems to me.
You might consider to use server-based solution for your workflow, like Adobe EchoSign, although it does not support digital signature. AFAIK similar competitors' solutions do not support digital signatures either.