Yes, this can be done. You will have to create a virtual folder in IIS or QVWS and then reference the folder in the URL. Like http://testserver/documents/test.pdf
Not sure what release of Qlik you are running, but there is a bug that will cause issue with the early releases of 11.20 SR12 that will cause issues with the URl
You can also do it with the help of having all emailid listed in excel and simply have the list loaded as Island in your application. Look at the below example -
You can to distribute Sales pdf to 10 users then follow the below steps;
1. list all the users in one excel and name the column Sales Users list
2. Load the excel in your application
3. Go to QMC and select the respective application
4. Create a task and select sales pdf and look through the Sales user list fields which you have loaded through excel
With the help of above steps you will be able to send the emails to external users without doing too many things.
Hope this help.