Here we briefly explain the difference between the two tools.
You want to create a dimension that remains as an annotation in the PDF document.
The dimension is an annotation, like all other annotations created in PDF Annotator. It remains in the PDF document when you save.
You can dimension distances and areas.
You just want to quickly take a measurement from a drawing. The document should remain as it is.
The measurement result is only temporarily displayed in the document and disappears again with the next click.
You can measure distances, perimeters, areas and angles.