Inserting pin/observation with x,y coordinate in a PDF drawing

Question

We use PDF drawings to let users in the construction industry insert errors, deviations, observations, etc. into floor plans etc. Today we convert the PDF to a png/jpg to get x,y coordinates in the image. This gives us the possibility to insert a observation "pin" on any mobile device, PC or Mac, and show it on another device on the same location in the drawing. Converting the PDF to a image either reduces quality or file size. My question is: How can we insert our observations directly into a pdf in our mobile/web apps, and keep it in the exact same location when opening it in different devices (different screen sizes and resolutions) The files should not be to big neither, as they are used on mobile devices in the field.

Answer 1

First thought - use two systems of coordinates - global(independent) and local(dependent of actual device). For example you can keep global pixel coordinates and after have some helper function on each platform to translate those to local PDF coordinates.

Hope this helps. If not please add some actual code of your current coordinate calculation.

Answer 2

You don't need to convert to image to add "pins" to a PDF on mobile. If you use the Adobe Reader (it's free) on both desktop and mobile, you'll be able to add an icon with a comment... even in the form of an arrow or pin to your document. The comment will then appear in the same place on the PDF in all Readers. If you previously had set the geo-spatial location on that PDF, you'll even be able get the position of the pin in real-world units, measure the PDF in real-world units, and create a report of the pin locations with their longitude and latitude.