Diagnosis
The Epson WF-2860 has two main places where default paper size can be set, and the one in use depends on your print source. The printer itself stores a hardware default for direct operations like copying and faxing. Your computer (Windows or Mac) holds separate, often overriding, software defaults for jobs sent from that device.
How to Fix It
To change the default universally, you must configure both the printer and your computer. First, on the printer's control panel: Press the Home button, navigate to Settings > General Settings > Printer Settings, then select Paper Size. Choose your new default (e.g., Letter, A4) and press OK. Press Home to save. Next, for your Windows PC: Go to Start > Settings > Bluetooth & devices > Printers & scanners. Click your WF-2860, select Printing preferences, and set your preferred paper size under the Main tab. Click Apply then OK. On a Mac, open System Settings, choose Printers & Scanners, select your printer, click Options & Supplies, then Driver, and set the default paper size there.
If That Didn't Work
Individual applications (like Microsoft Word or your web browser) often have their own page setup or print dialog settings that can override system defaults. Always check the print preview before sending a job. Also, ensure you are not selecting a different paper source (like the rear manual feed slot) that may have a different size assigned in the printer's paper settings menu.
Heads Up
For scanning, the default document size is usually set separately within your scanning software, not the printer's hardware settings. If you primarily print from a mobile device using Epson Smart Panel, the paper size default must be adjusted within the app's print settings.