Opened PDF in Photoshop Elements 2022, but background is Grey Checkerboard, what do I do?

I use Adobe Photoshop Elements 2022 extensively for specific tasks, but overall I'm no expert. Reciently, I had a task were I wanted to do some easy editing to instructions for a product. Those instructions are in PDF format. I understand that Photoshop Elements 2022 has the ability to edit PDF files.

I found and followed the instructions for opening a PDF in Photoshop Elements 2022 at the following URL. Opening files in Photoshop Elements (adobe.com) I scrolled half way down that page to that section, followed those instructions and was able to open the PDF in Photoshop Elements.

However, Photoshop placed all teh images and text of the single page PDF onto a Grey Checkerboard Background! I don't know what this means? There is nothing in the instructions at that point that talks about it? Attached is a screen shot of what I'm seeing after opening the PDF file.

Questions:

1) What does the Grey Checkerboard Background mean?

2) How do I get rid of it?

3) How do I edit the PDF product instructions?

I'm stuck, any help would be greatly appreciated.

I wish the Adobe instruction writers would assume that we customers are new to the product and would write help instructions that are complete and actually help. They know their product, and tend to assume we do also and as a result they leave out 80% of the steps that would actually be helpful.

James