Papermerge DMS is a non-destructive dms, which means you always have available original document regardless how many transformations (page rotations, deletion, document merges) you apply on the document.
Retention of the original is ensured because of document versioning feature. With each extra transformation you apply - a new document version is created.
Version 1 (one) of the uploaded document - is the original file i.e. document without any changes applied. Original document version is always available, regardless what operation(s) you apply to the document (except deletion of the document itself).