  We discuss the relation between the infrared singularities of on-shell
partonic form factors and parton distribution functions (PDFs) near the elastic
limit, through their factorisation in terms of Wilson-line correlators.
Ultimately we identify the difference between the anomalous dimensions
controlling single poles of these two quantities to all loops in terms of the
closed parallelogram Wilson loop. To arrive at this result we first use the
common hard-collinear behaviour of the two to derive a relation between their
respective soft singularities, and then show that the latter is manifested in
terms of differing Wilson-line geometries. We perform explicit diagrammatic
calculations in configuration space through two loops to verify the relation.
More generally, the emerging picture allows us to classify collinear
singularities in eikonal quantities depending on whether they are associated
with finite (closed) Wilson-line segments or infinite (open) ones.
