Embedding a Google Doc as an iFrame in your Swapcard Event is easy. Here's how to proceed:
You need to have a URL pointing to the PDF version of the document you want to embed. For this, you should start with this base URL:
and paste the URL of your hosted document at the end (replacing "PUT_THE_HOSTED_URL_HERE").
If you'd like to host the document on Swapcard servers, go to Studio → Content → Documents and Links, where you can upload your document and use the URL automatically generated.