Choose Edit > Insert Blank Page (Command+Option+B). A blank page will be inserted after the current page. Note: To bypass the stationery picker when inserting multiple blank pages with the same stationery, choose Edit > Insert Blank Page Again or copy and paste pages. (Creating Blank PDFs).

Nitro PDF Pro includes extensive AppleScript support so that it's possible to automate the PDF manipulation process.

Open the two PDF files that you want to combine. Set the Sidebar to show Thumbnails in both PDFs. Show Thumbnail view in the Sidebar by clicking on the Sidebar button

Click the down arrow next to the Annotate button

The default view in the application is Page View, where a Single Page is visible at a time. The other option is Facing Pages view where two pages are visible at once, like a book. Change between these views by clicking on the Sidebar item in the toolbar sidebar button or via the View menu.

View > Page Numbers is turned on by default. Notice a small gray (or blue) box with a page number in the bottom right corner of each page and thumbnail.

Split the screen into two panes to compare different pages of a document side by side.

Go to the View menu for the rotate page options:

View > Pages Right-to-Left is turned off by default. It is only active in the Facing Pages view and allows facing page order to be rearranged for reverse-viewing, such as needed in the Japanese language.

Reverse the order of pages, so the last page is viewed first, and the first page is viewed last. To reverse pages, choose AppleScript > Reverse Pages.