to access the documents easier, you can create hierarchy categories and link the documents to the related categories.
it can be used for these purposes:
- Related Products
- Related Process
- Organization Units
- Implemented Standards and systems
to create a new category, click on a 
button from the action bar, and fill the required fields then click on a
button.
if you leave "parent" empty, a new hierarchy will be created, otherwise, the item will be a sub-category of the selected "parent" category.
"Index" helps to get a customize ordering for the list of categories.
To Modify a document type, select it from the list first, click on a 
button, do the modification and then click on a button.
Note: if the selected document type is used in any documents, you cannot change "Abbreviation".