The design of Adobe currently makes you click twice to view a pdf whenever more than one pdf is currently opened in Adobe. This is because Adobe has been designed with windows to recognize each pdf as another window of the program. Windows does this with all programs like chrome, excel, explorer etc. However, adobe is a paper viewer/editor program and all opened pdfs should be coded as tabs under one program because the primary purpose is for viewing. Other programs like excel are for input, explorer for browsing and opening, but adobe is for viewing and the pdfs should be similar to tabs on an excel sheet. Excel opens with one click but has many tabs at the bottom. If you want another example using pdfsD, download "Drawboard pdf" app and see how nice it is to click to open the program once and see the document you last had opened.