I usually leave Location Services on my iPhone and iPad turned on. However, I must have turned it off on the iPad for some kind of test and neglected to turn it back on before trying to copy a screenshot to Dropbox for later use. You can see the warning I received from Dropbox that: Dropbox needs location access.
The question is why does Dropbox need my location just upload files? Fortunately, Dropbox itself provides the answer which popped up on my iPad and is also available on their website.
The answer is iOS Location Services must be left on in order for Dropbox to preserve the information in photos (including screenshots) when uploading the files to its servers. Leaving Location Services off may also be a fast way to strip off geo-location information from a photo if you want to do that.
The Dropbox app itself does not use location data in any way nor does it directly access your GPS device.
As a feature of your iPhone or iPad’s camera, every time you snap a picture or take a video, it will save GPS data to the file so that other applications (iPhoto, for example) can show where the photo was taken. However, for Dropbox to be able to access your photos without stripping this data from the files themselves, Apple requires owners to authorize access to its location services. By permitting Dropbox to access your photos this way, the Dropbox app can upload your pictures unaltered to your Dropbox as if you were using a cable.