If you want to add an image to the existing page, use the image button in the toolbar of Notepad+.
At the same time if you wish to open a pdf or an image in the app use the “Open In” option. Note: “Open In” feature is available for iOS 7 and higher.
1. Select the necessary pdf or image (png, jpg) in the app where it’s stored and tap the share control, then tap the “Open In” icon.
2. Scroll to Notepad+ and tap the app’s icon.
Notepad+ will launch creating a new notebook with the file used as a template.