The four platforms reviewed here differ significantly in what they can actually do with a PDF document. PDFelement is the only one offering genuine text-layer editing and OCR. Skim and PDF Annotator are annotation-focused tools. Xodo covers cross-platform annotation and basic workflow tasks with strong mobile support. Understanding these boundaries is essential before selecting a tool for a specific workflow.
Features are assessed based on publicly available documentation for generally available product editions. Where capabilities vary by tier, this is noted. Always verify with the vendor for your target version before making decisions.
Only PDFelement in this group supports modifying the actual text content of a PDF — rewriting sentences, changing paragraph structure, or editing fonts directly within the document layer. Skim, PDF Annotator, and Xodo work through overlay: they place annotations, text boxes, or markup on top of the document without modifying the underlying content. For workflows involving document correction or content updates, this distinction is decisive.
OCR converts scanned document images into searchable, selectable, and editable text. PDFelement includes OCR as part of its standard feature set, enabling full-text search and editing of scanned materials. The other three platforms do not include OCR — scanned documents remain as image-only files that cannot be searched or edited within those tools.
All four platforms support annotation, though with different depth and tool sets. PDF Annotator leads in handwriting and stylus-based markup — it was designed specifically for tablet review workflows. Skim offers comprehensive academic annotation tools including linked notes and reference management integration. Xodo provides clean annotation across mobile and desktop. PDFelement includes full annotation capabilities alongside its editing toolset.
Security capability is heavily skewed toward PDFelement in this comparison. PDFelement supports AES encryption, password-based access control, permission restrictions, redaction, and digital signatures. Skim and Xodo offer basic password protection without deeper access control. PDF Annotator does not include encryption or redaction tools — a notable gap for users handling sensitive documents.