In-house sharing of files... Companies of nowadays would use "Cloud storage". (Besides, there used to be "File servers"...)
However, in cases where file sharing "with an associated company or an agency" or "in collaborative project", there will be troubles since the other party is not "In-house". Suppose if you share by "email attachment", there will be problems like, not being shared until demanded, or annoyed with unnecessary files, or hesitate to share for not being requested. (In the first place, there are anxieties in terms of security in email protocol.)
For those cases, you ought utilizing accounts of Google, which one billion people use.
Create a folder for the project in "Google Drive", and add "Google Accounts" of all the members of the project team in Share setting of the folder.
(And make a wish that every member has got an account...)
The following is a mechanism to upload files that have been approved through team Workflow, to "Google Drive" automatically.
If some members of the team were users of "G Suite" (Google Apps) and "external sharing' was permitted, you would simply use Questetra standard [Service Task (Google Drive)] (M229). Whereas, in this case here, it is assumed to be operated with common accounts of gmail.com / googlemail.com.
[File Approval flow]