You can use your iPhone/iPad camera to scan a document and convert it to a PDF file.

First you can take a photo of each page of the document with your iPhone/Pad camera.

Then open Save2PDF and tap on the 3 lined button in the top left to show the left side panel.

Then tap on the 'Images' button in the left side panel.
You may have to use the photo album folder button in the toolbar to select the album that shows the new photos. The 'Recents' album should show the document images.

Tap on each document image you have added to show a checkmark on the image icon. Tap to select the pages in the correct order.

Tap the PDF button in the top right corner of the screen to show the PDF conversion screen.

Then you can tap on the save button to choose a name and location to save the new PDF file.