Last Update: 7/1/2018
First, you must bring both graphs into the same project. and there are two methods presented here. Read through each method and decide which one you prefer. Then, read through "The Final Step" to complete the merging of the graphs.
You may want to read FAQ-427 How to bring in data from another Origin project?
Open one of your two projects, and select File:Append. Next, select your second Origin project from the File Open dialog box and press OK. This second file with all its worksheets and graph windows will append to the open project. Any windows with duplicate names will be renamed. For example, Data1 would be renamed Adata1. Then, an Attention box will appear, informing you that duplicates were found and renaming has occurred.
Open one of your projects, activate a Graph window and select File:Save Window As to save the Graph window as an OGG file for later use. Repeat for each Graph Window of interest and for each Project file. You can open these OGG files into any Project by using File:Open and selecting OGG from the Files of Type drop-down list.
Now that the windows are in one project, you can merge your graphs onto one page by select Graph:Merge Graph Windows.