Link profile does not show obstacles such as forest
The path profile terrain data is primarily using the SRTM or Aster data sets, which map the top of the landscape including its land cover, which means that significant areas of land cover such as forest and urban areas may be incorporated into the terrain height. The SRTM data collection happened in February, a period of minimum leaf cover for northern latitude deciduous forests. This needs to be considered when setting the heights for each of the clutter classes for a given area.
In addition you can also enable clutter (under Project Properties), which will show types of land use and allow heights to be allocated to each clutter type. Depending on where you are in the world this clutter data has different resolutions and hence its accuracy in mapping areas of clutter varies depending on the extent of each clutter type. Please see Path Profiles — Cambium LINKPlanner Online Help (5.6.8) for more information on the mapping data used within LINKPlanner.