Upload a finished letter (identical content, no mail merge)
create_letterUpload and normalize a FINISHED, ready-to-mail document to PDF. Choose this when the content is final and IDENTICAL for every recipient — including when you mail the same letter to many people (just quote/pay once per recipient with the same documentId). The exact bytes you give are what gets printed. Use create_template instead only when the content must vary per recipient via {{fields}}. Returns a documentId, the stored page count, byte size, and source format. Free; no payment required.
Provide the document EXACTLY ONE way: content (inline text, for html/markdown/text), contentBase64 (base64-encoded binary, for pdf/docx/image), or url (a publicly reachable URL the server fetches). Supplying none, or more than one, is an error. Maximum upload size is 31457280 bytes (~30 MB); output page size is US Letter.
Any {{...}} text is printed LITERALLY here — it is NOT treated as a merge field. If you want personalized mail merge across recipients, use create_template instead.
Reserved address zone: a recipient address block is printed over the top ~3 inches of page 1, so the server reserves that space for you automatically. For text/html/markdown/docx, page-1 content is pushed below the block (content may therefore flow onto an additional page); for pdf and image inputs, a blank first page is prepended. As a result the returned page count — and the selected-provider cost behind the resulting quote — can be higher than your source document (e.g. a single-page PDF is stored as 2 pages). You do NOT need to leave the top of your document blank yourself. See the postagent://formats resource for per-format details.
Input Schema
| Name | Required | Description | Default |
|---|---|---|---|
| url | No | Public URL the server will fetch the document from. Provide exactly one source. | |
| format | No | Source format. Inferred from contentType/filename/content when omitted; inline `content` with no format defaults to text. | |
| content | No | Inline text content (html, markdown, or text). Provide exactly one source. | |
| filename | No | Optional original filename; used to help infer the source format. | |
| contentBase64 | No | Base64-encoded binary content (pdf, docx, image). Provide exactly one source. |