Quickly add a preview image for your Reader Post which displays your PDF document.
Step 1: Click the white [Plus +] icon in the top right corner of your Topic banner to create a new Post.
Step 2: Choose the PDF option and Source you'd like to Publish you're PDF to.
Note: Be sure to select the Source that lives in Topic where you aim to Publish your PDF. Learn what a Source is here.
Step 3: Upload your PDF and Select your custom image file.
If an image is not chosen, an image of the PDF's first page will show in your Topic.
Step 4: Click [Create] in the bottom right corner of the pop-up.