You can insert inline frames (iframes) to show PDFs or URLs within an HTML page. To insert an iframe, open a topic in the Design Editor and place the cursor where you wish to insert the iframe. From the HTML section of the Insert tab, click on the Text Box dropdown menu and select Iframe.
Enter a name in the Name field and click on the Browse button to select a URL, HTML file, or PDF file to link and then click OK.
You can optionally set border options in the Border tab.