SPENDS CREDITS: merge two or more PDFs into one, in the order given, optionally taking only some pages of each. The merged file is stored in Doxis AI.dp storage and returned as a file id. Uses your own Doxis AI.dp (Klippa) credits: billed per request or per page depending on the service (extra components in a configuration can add cost), at your project's price (Billing → Pricing in the platform); a new account starts with EUR 25 of free credit. Each document is one of url (public https), data_base64 or file_id. POST /document_toolkit/v1/merge.