[lars-b2018]

PDF is great because of its ability to present a print oriented view of any type of information, packed in a document container in an efficient manner. This is the design goal of the format. It is the source application's responsibility to manage the semantics of the document scope, where edits to the represented information can potentially cascade across the document in non-trivial ways (think Excel for example). PDFs CAN be edited today, but those edits are made by tools that just change the visual layout vs. the information structures represented by the document. It's a rather difficult problem to overcome if the PDF format now must contain rules about the underlying information structure itself in order to maintain a consistent representation in the document.