Hi,
There is no 'trial' for Acrobat Standard. Trial is only provided for Acrobat Professional. What you can do is provide Acrobat Professional trial to all the users. The users who require the software and want to use it, you can provide them Acrobat Standard instead through the method provided by Ben earlier. In this case you need to serialize the install and deploy it using a GPO\SCCM to the concerned person.
Thanks,
Vinod