In this case, I'm going to "go to list" and view all 41 skill ratings this volunteer has - and look at the one called licensed RN.   I click on the Skill Rating ID to get to the skill rating record:

Copy the attachment Url and then paste it into a new browser tab.  That URL will open or download the attachment that was uploaded in association with the Skill Rating Documentation in the list.  In this case, I'll see the Licensed RN's certification that was uploaded.

If you wish to make it available to staff in Salesforce as well, update the Staff profile to give read only access to the "Skill Rating Documentation" object.

First, you'll need to create a new custom report type by going to setup / Create Report Types and clicking on New Custom Report Type.

Primary Object = Skill Ratings
Secondary object - with or without records from Skill Rating Documentations.

Click on Edit Layout, and then use "add fields related via lookup" from the skill ratings object, to add all the fields from the contact record.  (Make sure that you new custom field "View Documentation" is included in the available fields in the Skill Rating Documentations object for this report type.)

Use the filters and fields as noted in the above illustration.   Group by Contact Full Name.

Do a Save As to create a report with a new name - and add the cross filter  "Skill Ratings WITH Skill Rating Documentations".     This will exclude skill ratings that don't have a related documentation object.

These reports will give you an overview of all the skill documentation that is available. (instead of having to go to individual contact records to drill down to each skill rating and see whether it has a related skill rating documentation object!