INCREASING DPI TO PRINT QUALITY

I have a number of images that I wish to include in a book - they have been taken on a phone but the DPI needs to be increased to 300 for print quality - I also need , where applicable, the identity of the individuals to be obscured. At the end of this work, everything needs to be entirely legal and above board so please only apply to help with this project if you know the rules about publishing images - they are all perfectly innocent images so there is nothing to be concerned about on that score. Thank you. I have added an image below to give you an idea of the challenge - I do not need the images to be made to look nice in any way - they are meant to be authentic so don't be concerned about that. This is for a book on supplements so there will be images of people's health conditions.