Genius Scan should be your go-to application for document scanning.
Genius Scan is a very user-friendly software that scans everything, adjusts and corrects the perspective (in fact, you can tilt your phone to avoid unwanted shadows on your documents!) and gives you the power to enhance it in black and white for better readability.
You can also scan documents in batches so you can add pages quickly and merge them together. Genius Scan seamlessly allow you to create JPEG or PDF files with multiple pages as well as organize all your scans in folders and export them to your subscribed cloud service.
You can categorize your documents with tags, then use the search field to instantly locate them.
Genius Scan is FREE yet has no limits on the number of files you can scan, and generates documents in full resolution without any watermark.