This article outlines why DocumentsCorePack need Application Permissions.

If you're creating a service and you have to choose the connection profile, there are several options.
If you use the Server2Server-connection, you need to activate the following:

Figure 1: Permissions requested

1.) Access to common data service

This means, that we can read the CRM data in your name
(so we can ensure, that user specific settings are applied to the data retrieved, like number & datetime
formats)

2.) Read and Write your files &
      Read and write items in all site collections &
      Read and write items and lists in all site collections

These are the SharePoint security requirements to be able to fully use the Dynamics SharePoint integration.
When DCP is linked with Dynamics SharePoint Integration, DCP will create lists, folders & files in the
SharePoint location as Dynamics would create them.

3.) Sign in and read user profile

This is required to login as the user in dynamics and also for some of our licensing options. 

That’s it! We appreciate your feedback! Please share your thoughts by sending an email to support@mscrm-addons.com