When you upload a document, one or more preview pages are automatically selected based on the document's size and shown to potential customers. You can adjust the number of preview pages by following these steps: go to Uploads → click on the three dots next to your document → Edit.

When deciding how many pages to preview, keep in mind that customers base their decision on the title, available information (like the description), and what they see on the preview pages. So, choose carefully!

For more details on this topic, check out the support page: What Do I Show on My Preview Pages?