Merge PDFs - Forme

POST /v1/merge Merges PDFs into one document, in array order. See the Merge API reference for what is and is not carried over from the source files. Each successful call is one operation.

Request body

Field	Type	Required	Description
`pdfs`	`string[]`	Yes	Base64-encoded PDFs. At least 2, at most 20.

The whole JSON body can be up to 20 MB, base64 included.

curl -X POST https://api.formepdf.com/v1/merge \
  -H "Authorization: Bearer forme_sk_abc123..." \
  -H "Content-Type: application/json" \
  -d "{
    \"pdfs\": [
      \"$(base64 -w0 invoice.pdf)\",
      \"$(base64 -w0 terms.pdf)\"
    ]
  }" \
  --output combined.pdf

const res = await fetch("https://api.formepdf.com/v1/merge", {
  method: "POST",
  headers: {
    Authorization: "Bearer forme_sk_abc123...",
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    pdfs: ["invoice.pdf", "terms.pdf"].map((f) => fs.readFileSync(f).toString("base64")),
  }),
});

fs.writeFileSync("combined.pdf", Buffer.from(await res.arrayBuffer()));

Response

200 OK, Content-Type: application/pdf. The body is the merged PDF. It is not saved to Documents. Fewer than 2 or more than 20 PDFs returns 400.