What Does Flattening a PDF Actually Mean?
PDF documents often contain interactive layers: AcroForm fillable text fields, digital signature widgets, comments, and annotation markups.
Flattening merges these dynamic overlay elements directly into the static page drawing stream, transforming editable form values into immutable vector or raster primitives.
Flattening prevents recipients from modifying form entries, but it does NOT remove underlying metadata or creation timestamps.
What Metadata Scrubbing Does Differently
While flattening addresses the visual presentation layer, scrubbing targets the document control structure: Info dictionaries, XMP metadata, embedded thumbnail caches, and application-specific /PieceInfo records.
A document can be flattened yet still leak author and workstation information, or it can be scrubbed while maintaining its fillable form fields.
The Hazards of Using "Print to PDF" as a Workaround
Many users attempt to sanitize documents by printing them through virtual PDF printers. However, this often causes text rasterization degradation, alters embedded color profiles, and injects new printer driver metadata into the output file.
True document hardening combines interactive form flattening with surgical binary metadata purging.