How to get a post plumb using a bolt down anchor?

[mh]

I want to place some posts on existing concrete using Pryda bolt-down post anchors. https://www.bunnings.com.au/pryda-post-anchor-bolt-down-w-washer-100mm-m10_p1070068 The concrete is slightly sloped but the post needs to be plumb. What is the best way to get it plumb? I have done a similar job in the past just using window spacers under the plate, but that was just for a freestanding screen, nothing weight bearing. I want to do it a bit more professionally this time. Thanks. 

Is there a better way to get it plumb?

[SMOKOTIME]

Sorry I'm just a cranky old Engineer who is very tired of support people who have no practical experience.  Their support teem need to set a few posts and see how bad their advice is. 

There is NEVER any guarantee that the foot on a post is square to the upright and any discrepancies will be magnified over the length of the post. 

There is NEVER any guarantee that the pad will be troweled perfectly level or even flat and any discrepancies will be magnified over the length of the post.

He did mention LOAD BEARING and nobody asked what the load is what it is being clad with and what wind exposure it has.

Better to set the post properly and level with a spirit level and then pack to achieve the best compressive strength. 

Otherwise you may as well use tile grout or plastic wedges over an expansion joint.