How to use image in file attachment attribute on the quote in proposal document (pdf)?

Summary:

We would like to allow the sales user to upload an image onto a file attachment attribute on the quote header. This image needs to be used on the proposal. Since this would be in jpg or png format, the document designer is unable to generate the image on the proposal pdf.

I have considered the workaround of asking the sales team to either upload the image as a pdf file or share an external url for the image. Please let me know if there is any other way to implement this.

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