Users in Advanced and Admin-type user classes that have the Manage Documents permission can add/edit documents and adjust viewing access using the Document Customization page in Manage > Administration > Documents > Document Management.
On the Manage Documents page you can add different categories for your document repository to keep everything organized.
To add a new category, click on the + Add New Document Category button at the top right and you will see this popup dialog:
Filling in the name field will give a title to each category and the description can tell users what type of documents they might find within that category. Additionally you can use the combination of groups and user classes to narrow down exactly what users will be able to see which categories of documents. This information can be edited again once the category has been added by clicking Edit Category.
After the category has been added you can click the Add/Remove Documents and be brought to this page to begin adding labels and documents within this category:
Add a new label by clicking + Add Label and enter in a new Label name:
The next step is to add your documents. Click the + Add New Document button to set a name, description, set user class viewing permissions, and upload your document:
Making mass updates to the user class permissions of the documents within a category can also be done by clicking the checkbox next to each document you already have uploaded and clicking on the Update Selected Documents button and using this dialog to update them:
Note: Categories, Labels, and Documents can all be dragged/dropped to be in the order that you want them to be displayed in.
To see how your users would see the documents added/edited from this page, visit this article: Viewing the Documents page.