The license file contains details such as the product name, number of developers it is licensed to, subscription expiry date and so on. It contains digital signature, so don't modify the file. Even inadvertent addition of an extra line break into the file will invalidate it. You need to set a license before utilizing *GroupDocs.Editor API* if you want to avoid its evaluation limitations.
Calling License.SetLicense multiple times is not harmful but it wastes processor time. If you are developing a Windows Forms or console application, call License.SetLicense in your startup code, before using GroupDocs.Editor classes.
When developing an ASP.NET application, you can call License.SetLicense from the Global.asax.cs (Global.asax.vb) file in the Application_Start protected method. It is called once when the application starts. Do not call License.SetLicense from within Page_Load methods since it means the license will be loaded every time a web page is loaded.
Applying License from File and Stream