So if you need multiple documents for 1 Employee, you would usually achieve this by having your Dataverse form have the Employee details fields, and a Subgrid on that form for the documents.
Given the above, for Power Pages (and because subgrids don't render until after the record is created). You may choose to have 2 Tabs on your Dataverse form (1 for Employee Details, the other with the Subgrid).
You then create 2 Basic forms (1 for each Dataverse Form Tab, or 1 for each Dataverse form depending on how you approached it) - note: the Site Designer has less options than Portal/Power Pages Management App and will default to showing the whole Dataverse Form (not specific Tabs).
For your Basic Forms, there are settings for Redirecting On Success (i.e. record saved, go to a different page), and also for receiving the ID (GUID) of the record for the Basic Form to start with (Record Source Type on the page but above where the link I posted earlier is to). So you basicaly configure 1 Basic Form to send the ID, and the other Basic Form to receive that ID (by default the system usually uses the paramter 'id' but you can use a different name, you just need to set the same value in both the redirect/send and query string paramter).
If you get that working, you will create on Page 1, load Page 2 and see the Subgrid (but you then need further configuration to allow create and edit of items in the subgrid - this can be done by adding a metadata record to the Basic Form that has the Subgrid on it, and setting its Type to Subgrid https://learn.microsoft.com/en-us/power-pages/configure/configure-basic-form-metadata#basic-form-metadata-properties)
Also, if you search online you will find Videos etc showing how to do it.
