Add workflow privileges section

content/docs/workflows/_index.md

@@ -30,7 +30,7 @@ Here are the basics.
 
 5) Choose when the workflow should be run. Use the option _manually only_ if for example you want the workflow to run on a button press. Alternatively, set the frequency you wish the workflow to attempt to run. This determines how often the system should check whether there are records to process. The check is only done if there's been a relevant change to the state of the system e.g. records edited since the last workflow run. However all workflows with a check frequency are guaranteed to run at least once a day.
 
->Using _24 hours_ plus a filter on a 'd'ay of the week' calculation allows you to run weekly workflows.
+> Using _24 hours_ plus a filter on a 'day of the week' calculation allows you to run weekly workflows.
 
 For 24hr workflows you can optionally set a specific time of day for them to run.
 

content/docs/workflows/advanced/_index.md

@@ -17,3 +17,11 @@ They will contain success and failures of past runs as well as the next time the
 
 ![Viewing the logging history of a Workflow](/workflow-history.png)
 
+## Workflow privileges
+
+If workflows are run in the background on a timed basis, e.g. every 10 minutes, they don't need privileges on the tables they act on. They effectively run as a 'system user', not a real person.
+
+If workflows are however kicked off by a person pressing a [workflow button]({{<relref "workflow-buttons">}}), or [creating or opening a record]({{<relref "workflow-on-create">}}), they run with the privileges of that user.
+
+That can be overridden by ticking the option *Allow workflow to act on any table* when editing the workflow. If for example you have a workflow button which creates a new purchase order when the user presses it, but the user has no privileges on the purchase orders table, that option will allow the workflow to run successfully.  
+