# Adding Assets to PDF

[Assets](../../variable-data-types/the-asset-data-type) are Airkit's representation of files. They can be created, manipulated, and transmitted via Data Operations in [Connections Builder](../../studio/builder-bar/connections-builder).

Typical use cases include branding, embedding of photo IDs for identification purposes, and stamping signatures.

To add Assets to PDFs, the [Fill PDF Form](../../data-operations/the-fill-pdf-form-data-operation) Data Operation is used, which takes a blank PDF template and merges values into form fields. The PDF is then filled with the values stored in the assets that are obtained through the `download_url` property.

## Using the Fill PDF Data Operation

If you have a form which resulted in an image stored as an asset, then this asset can be written into a PDF.

To do so, create a Data Flow to pass the Variable that contains the downloaded asset (`download_url`) through a [Fill PDF Form](../../data-operations/the-fill-pdf-form-data-operation) Data Operation to the PDF we need to get filled.

![](https://3088276961-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FC6qMwMGWBgxnN70QsDuH%2Fuploads%2Fgit-blob-72a8bf36a54121670cb52f77695985f227152b6c%2Fadding-assets-to-pdf-v182-0.png?alt=media)

## Example: Writing signatures to PDFs

To write the signature into the PDF, create a Data Flow to pass the Variable that contains the downloaded asset (`download_url`) using the Fill PDF Form Data Operation as shown above.

Then add a Global Variable for the output and then trigger the Data Flow from a Button or Action. Pass the following Values:

![](https://3088276961-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FC6qMwMGWBgxnN70QsDuH%2Fuploads%2Fgit-blob-6910a59279cb2c7401002a9edc5db59d3093915e%2Fadding-assets-to-pdf-v182-1.png?alt=media)

This way, the saved typed signature gets inserted into the PDF form.
