One of my favorite apps for viewing and marking up PDFs iAnnotate has added a new feature with the latest update.
Now, you can view and mark up two PDFs side by side.
To invoke the function, open two PDFs. Each will have its own tab. Tap and hold on one of the tabs. One of the options will be “Two Document View.” Tap on that and the screen will split each PDF into its own half size view.
To exit this mode, tap on one of the tabs and tap on Exit Two Document View.
This feature allows you to view and independently mark up PDFs side by side.
iPad Notebook 