I know a solution which might be helpful. You can merge all of the pages of a PDF into a single page as a image file. Try using PDFelement to fulfill your need. I’ll show you how to do that below. Open your PDF file with PDFelement, and then click on “To Others” and choose “Convert to Image”. Here a pop-up conversion window will show up. Click on the “Settings” button. Here, you should choose the second option “Adjoin all pages into one single image”. Click on “OK” then. After the conversion, you’ll have all of the pages of your PDF file merged into a single image. This article might be helpful. How to Merge PDF Pages into a Single Image
Using PDF Element. The image size and resolution can also be improved.