In PLAXIS 2D 2010, it is not possible to select force envelopes in a standard report, but there are some steps to get the desired plot into your report.
This has been fixed since PLAXIS 2D 2011.00. By activating the Advanced selection in step 5 of the report generator, the envelope option for the forces can be selected.
In order to get force envelopes in the report in PLAXIS 2D 2010: