Hello, it looks like you want to replace all your word files with PDF version but metadata should not be changed. This can be done easily but, as an expert, I will make sure that, these change of file types don't impact the search, rights on file if shared with any user etc.
I provide these as questionnaires to my client when they come with any business problem.
Also, I would like to ask you that this replacement of files is one time, by any program or manual?