Microsoft provides as a feature-on-demand. The offline installation source can be a CAB file named something like:
The standard GUI-based "Turn Windows features on or off" method often ends with: cab file for .net framework 3.5
This is the standard method for enabling the feature using a local CAB source. Microsoft provides as a feature-on-demand
DISM /Online /Enable-Feature /FeatureName:NetFx3 /All /LimitAccess /Source:"C:\DotNet35" cab file for .net framework 3.5
A password will be e-mailed to you