uograding free version to pr

Hi, I am using the free version, if I buy the pro version will all data like agenda, contacts and archief remain?

Pro version allows you to have more than 2 email accounts attached to emclient.  All one needs to do is enter the license number to get the pro version.  
Note version 6  and version 7+  have different formats  so as long as you have the 7+ version you should have no impact.
But just to be safe run the emclient backup
If you intend to buy the pro   update to the latest 7.2 version first then buy the pro

Again always run the backup first  and make sure you have your current version stored away with the free license number saved in a secure place on your pc.

In case you need this
https://www.emclient.com/release-history

Menu
File
Backup  

Hopes this helps     User

Upgrading to the Pro version will not affect your data in any way. It is exactly the same application so there is no need to install anything. All that happens is when activating using a Pro License key, a few extra features will be enabled.

how i can active pro version for 10 computers 
please help me about that 

First you need to purchase your Pro Licenses. You can do that at https://emclient.com/purchase-em-client

Once you receive the license activation key, you can go to each computer and activate it in Menu > Help > License. You will receive a single activation key that you can use on all the computers.