If you see a triangle with an exclamation point in place of the pages on the right side of the tab this means you have too many files open and app performance may be affected .
When the multiple tabs along the top turn into one long tab with an exclamation point the app is warning you there are too many documents open and the app's performance could be affected. In this state it is recommended you close as many documents as you can only leaving the documents you are currently working on opened.
To close documents tap the "x' next to the name. The document will not be deleted and can be found in the iAnnotate library when needed.