This example uses a set of Categories that are organised as shown opposite.  This is a just a subsection of all the Categories on the site.

Specifically in ths example we are going to set the Access level for all the Downloads that belong to the Nodus Website category and all its various levels of Child categories to the Registered view Access level.

As the first step in the back end go to Downloads and use the Select Category filter to only list the Downloads that are in the categoty chain starting at at the highest category level that is to be changed, in this example it is the Nodus Website category.

This gives a view such as shown below.  Note that after the list appeared then all the Downloads were 'selected' by 'ticking' the Title column.

The number of Downloads that may be selected is limited by number shown on the downloads summary screen. This value is set at the top righthand side of the summary screen.  Remember to set this to an appropriate value.  Clearly 'All' is a safe choice.

The next step is simply to click on the 'Batch' button

This brings up a modal window as shown opposite.  All we need to do is use the 'Set Access Level' pulldown to select the required Access Level.  Leave the other options alone. 

Then click the 'Process' button.

Note: the other options, especially the move category one, could be used to re-organise the Downloads.