Old Adobe was better
In prior Adobe Acrobat versions scanned pages could easily be inserted into an existing file as a new first page. or between any two previously existing pages. That was excellent as I always add pages to the top of existing documents. That feature appears to have been stupidly eliminated. I want the old Adobe!
This functionality is still there. You can insert pages at any location you want. Follow the steps:
1. Open any file in Acrobat
2. Go to Organize Pages app
3. Click on “Insert → From Scanner” option
4. Select options to scan and click scan button
5. A dialog will come asking where to insert scanned pages. Now you can select any option suites you.
Also, at step 3 you can hover around pages where you want to add scanned pages, there will be a “+” button. Clicking it will add pages at that location only.
Please feel free to ask anything you want.