Numerous digital signatures

Hello,

i am currently working on a proposal to enable a small company to move away from paper based workflows. I believe Adobe can assist with this. However a constraint on the proposed system is that it needs to be secure and never connected to the Internet.  Basically a PDF shall be commented on by one user and sent to anotheir user for approval. This PDF will go though a chain of persons to ensure all is in order.  is it possible at each stage of approval, a user can digitally sign and time/date stamp the PDF? I have tried I'd, however the PDF becomes locked after one signature. Ideally I would like 4 users to sign/approve the PDF before it is finally signed off and no editing is allowed, is this possible. 

Thanks,

Joanne

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