Creating a process that would prevent a user to move an opportunity from one stage to another if no document is attached to it

Case

I am trying to create a process, which has to prevent user to move an opportunity from 'Define project' to 'Proposal' stage if no proposal document is attached to it. How can I delete a process?

Solution

The easiest way to check if the document attached on the certain stage and prevent the opportunity from moving to the next stage is to do that within the case:

Then you can either add the simple task to be completed with the title like 'Is document attached?' or you can run a sub-process within the case to check if the doc is attached and depending on the condition move to one or another:

We also recommend you to check the articles about case designer to achieve your business goal: https://academy.bpmonline.com/documents/studio/7-11/case-management