The trick is old and works with any printer: print all the front sides first, put the stack back in, then print all the back sides. The two things that go wrong are the order of the pages and which way the paper goes back in. Both are easy to get right with a quick test.
1. Make two files
Open Odd or even pages and add your document. Choose Odd pages and Keep them, and download. Do it again with Even pages. Name the files fronts.pdf and backs.pdf so you don't mix them up.
If your document has an odd number of pages, the last sheet has no back. That's fine; just remember to take that sheet out before printing the backs, or add a blank page at the end with Insert blank pages.
2. Test with two sheets
Before printing 40 pages, print the first two pages of fronts.pdf. Draw a small arrow pointing up on the top edge of each printed sheet, and note which side is face up when it comes out of the printer.
Put those two sheets back in the tray and print the first two pages of backs.pdf. Look at the result:
- If the backs are upside down, rotate the stack 180° next time.
- If the backs printed on top of the fronts, flip the stack over.
- If page 4 ended up behind page 1, your printer outputs face up; reverse the backs file with Reverse pages.
Write what worked on a sticky note and put it on the printer. You'll need it again.
3. Print the rest
Print all of fronts.pdf, put the stack back the way your test showed, and print backs.pdf. Fan the paper before reloading it; sheets that just came out of a laser printer are warm and tend to stick together.
The opposite problem
If you scanned a double-sided document on a single-sided scanner, you have one file with all the fronts and one with all the backs, often in reverse order. Interleave PDFs merges them back into 1, 2, 3, 4, with an option for backs that were scanned in reverse.