The content is saved as rich text in the database and rendered in a group as text. This content also contains images. However, the screenshot saved does not show the image from the rich text. It also does not display the highlighted text. Below is the comparison of the group and the downloaded image.
Use and display in an HTML element ( not a separated text and image ) or within a rich text editor ( you can use CSS codes to remove the background, and borders color of a rich text editor to make look it solid )
The PDF Converter reads only HTML within a specific div element ( in your case it is a group)