When you take a picture of a paper document, take a screenshot of online documents, they will be saved as images on your mobile phone. What to do if you need to convert screenshot or pictures to text or PDF file? Today, we’re going to use a free PDF scanner, Simple Scanner, to convert screenshot to PDF, combine multiple images into a PDF file on Android phone.
Run the free document scanner app on your mobile phone. Tap the Menu button, three dots icon, at the top right corner to bring up the menu at the lower section on your phone screen. Then choose Import from Gallery, browse through your photo albums, screenshots folder on the phone and import them into the PDF scanner app. You can select and import multiple images to combine and convert them into one PDF file.

After that, you will have the options to crop image, choose color style, name the file before saving it. It is very easy and straightforward.
Scan documents to PDF directly using your phone
Other than taking pictures and then converting them to PDF files, you can directly scan documents to PDF on Android using this free scanner app.