Docparser works by building parsing templates: you map zones and rules to fields for each document layout. That gives fine control on fixed formats, and it has a large library of no-code integrations.
pdftojson skips the templates. You send a PDF and get structured data back, whatever the layout, plus a correctness check for financial documents that a template parser doesn't give you.
Where pdftojson is different
The trade with a template-based parser is setup and upkeep: every new layout is a new template, and layouts drift over time. pdftojson reads the document directly, so a statement or invoice from a bank or vendor you've never seen still comes back as structured data without building anything first.
And for financial documents it adds a check template parsers don't: it reconciles a bank statement's transactions against its opening and closing balances and flags any that don't add up.