PDF AutoSigner

Audience: Low-code Engineers

Skill Prerequisites: Actions, Forms, JavaScript

The PDF AutoSigner add-on lets users sign PDF files on a form with their own electronic signature token, which is protected by a PIN. The signing is done by the PDF AutoSigner app on the user's computer, not by the server. The add-on adds two actions and a form field that talk to that app from the user's browser.

note

These actions are part of the PDF AutoSigner add-on (PlantAnApp.Integrations.PdfAutoSigner). The add-on is installed separately. Its feature code is PDFSIGN, but in version 1.28 the actions and the field don't check it in your license. If you don't see the actions in the Documents group, the add-on isn't installed.

Choosing an action

Action	What it does	Use it to
Sign PDF	Signs a PDF with the user's signature token through the PDF AutoSigner app, and puts the signed file in an upload field. Forms only.	Let an employee sign a generated contract on a form.
Check if PDF Auto Signer is running	Checks from the user's browser whether the PDF AutoSigner app answers, then runs your JavaScript. Forms and listings.	Warn users to start the app before they sign.

The add-on also adds the AutoSigner Signature Dropdown form field, in the Single Choice fields. It lists the signatures available on the user's computer, so the user can pick the one to sign with. It has the Title When No Selection and Initially Selected settings of a dropdown.

To check on the server whether a file is signed, use Check PDF Signature from the PDF Generator add-on.

The PDF AutoSigner app

The PDF AutoSigner app is a separate program that each signing user runs on their own computer. It has access to the user's signature token and does the actual signing, so the certificate never leaves the user's computer. The app isn't part of the add-on package and isn't installed on the server. These docs don't cover installing it. Ask Plant an App for the app and its requirements.

The browser talks to the app directly, at a fixed local address. The server never contacts the app.

Request from the browser	Sent by	What the app returns
GET http://localhost:7521/api/sign	The AutoSigner Signature Dropdown field, when the form loads, and Check if PDF Auto Signer is running	The names of the signatures available on the computer, as a JSON array.
POST http://localhost:7521/api/sign	Sign PDF	The signed PDF. The request holds the PDF as file, and the PIN and signature name as inputDataJson, for example {"Pin":"1234","SignatureName":"John Doe"}.

The address and port are set in the add-on's scripts. You can't change them in the actions.

What each signing user needs:

• The app installed and running on the computer they sign from, listening on port 7521.
• Their signature token connected, and its PIN.
• A browser on that same computer. Signing doesn't work from a computer or device where the app isn't running.

Setting up a signing form

1. Add an AutoSigner Signature Dropdown field for the signature, and a Password field for the PIN.
2. Add a Single File Upload or Multi File Upload field to receive the signed file.
3. Add a button that runs Sign PDF. Set its File to sign to the file ID or path of the PDF, for example the output of Generate PDF.
4. In On Signing Result, show the user what happened and submit the form, so the signed file is saved.
5. Optionally, run Check if PDF Auto Signer is running when the form loads, and tell the user to start the app if it doesn't answer.

Things to know:

• Start the app before opening the form. The dropdown asks the app for signatures only when the form loads. If the app isn't running, the list shows one entry starting with error:. Start the app, then reload the page.
• Both actions run in the browser and end execution. No actions after them run. Put the follow-up logic in their JavaScript.
• The PIN goes through the server. The PIN field's value is sent to the server with the button click and back to the browser for the app. Don't save the PIN field in reports, and use HTTPS.
• The app decides how the signature looks. Sign PDF has no settings for its position, reason or location.
• Running isn't the same as ready. If Check if PDF Auto Signer is running gets an answer, signing can still fail, for example if the token isn't connected or the PIN is wrong. Sign PDF returns error code 2 in that case.
• Not for workflows. The signing needs the user's browser and computer, so it can't run in a workflow or scheduled job.

For all add-ons, see Add-ons.

Revised 10/02/2026