List a PDF's AcroForm form fields — names, types, options, current values, per-field maxLength where declared — plus a paste-ready fillTemplate object for pdf_fill and a hasXFA flag (hybrid AcroForm/XFA inputs lose their XFA layer when filled). A PDF with no fillable form returns count 0. Read-only: the PDF is fetched or read but never modified. Call this FIRST when filling an unfamiliar PDF, since pdf_fill rejects unknown field names and over-length values.

Fill AcroForm form fields in a PDF and save or return the result. Field names must exist in the PDF (use pdf_inspect first). All values are strings; checkboxes take "true"/"false"; dropdown/radio/optionlist values must be one of the field's options; text values must respect the field's maxLength from pdf_inspect. The source PDF is never modified. Returns the filled PDF written to output_path, or inline as an application/pdf resource when output_path is omitted; an existing file at output_path is overwritten. Encrypted PDFs are rejected with decrypt advice (common for government blanks with an empty user password), and a rejected fill writes no file at all.

Merge two or more PDFs into one, in the order given, and save or return the result. Source files are read only and never modified; an existing file at output_path is overwritten. Returns the merged PDF written to output_path, or inline as an application/pdf resource when output_path is omitted. This tool only concatenates whole documents: it does not reorder, rotate or delete pages within them, and it does not fill forms — use pdf_fill for a fillable form and pdf_invoice to build a document from data. An unreadable or rejected input fails with an error and writes no file, so a partial merge is never left behind.

Generate a complete, professionally laid-out invoice PDF from structured data — no template needed. Deterministic: the same input produces byte-identical output (safe to re-run). Note: without a paid PDFops key the output carries a small "Generated with pdfops.dev" footer line. Returns the invoice written to output_path, or inline as an application/pdf resource when output_path is omitted; an existing file at output_path is overwritten. Use this when you have invoice DATA and no document; if you already have an invoice PDF or a fillable template to populate, use pdf_fill instead.

Check the current PDFops API quota for the configured key: tier, limit, used, remaining, the billing period, and the reset timestamp. Read-only and safe to call before a batch to confirm there is headroom. Requires PDFOPS_API_KEY.