I tested just the exact example in the documentation with a PDF and after the file arrived it has 16KB of additional data appended to the total file size and Adobe will not open it because it says it is corrupted.

Happens every time, even when testing directly from the rule and uploading a file.

Here is the example I used to create the body

https://developer.laserfiche.com/guides/guide_importing-documents.html

Here is how it looks in my rule

--FakePlasticTrees
Content-Disposition: form-data; name="electronicDocument"; filename="File.pdf"
Content-Type: application/pdf
%(Name: File; Type: File)
--FakePlasticTrees
Content-Disposition: form-data; name="request"
Content-Type: application/json
{
  "template": "Email",
  "metadata": {
    "fields": {
      "Sender": {
        "values": [
          {
            "value": "sender@laserfiche.com",
            "position": 1
          }
        ]
      },
      "Recipients": {
        "values": [
          {
            "value": "recipient@laserfiche.com",
            "position": 1
          }
        ]
      }
    }
  }
}
--FakePlasticTrees

Where did the additional data come from that corrupts the PDF?