Apple LaserWriter 12/640 PS - Manual (Page 207)

4 Set your program to print lengthwise on the envelope.
On a Mac OS–based computer, choose Page Setup from the File menu, select
the Landscape orientation icon, and click OK.
On a Windows 3.1–based computer, open the Printer Setup dialog box and
select Landscape in the Orientation option.
On a Windows 95–based computer, open the print Properties dialog box and
select Landscape in the Paper tab.
5 Set your program to print using the multipurpose tray.
On a Mac OS–based computer, choose Print from the File menu, select
Manual Feed from the Paper Source pop-up menu, and click Print.
On a Windows 3.1–based computer, open the Printer Setup dialog box, select
the multipurpose tray from the Paper Source options, and click OK to close
the Setup dialog box. Choose the Print command from the File menu and
click OK.
On a Windows 95–based computer, open the print Properties dialog box and
select the multipurpose tray from the Paper Source option in the Paper tab.
6 When the printer’s Paper Out indicator light flashes, insert the first envelope and slide it
forward until it stops.
Insert the envelope face up (flap down) with the top edge to the right as it
enters the printer.
On a Mac OS–based computer, if Background Printing is turned on in the
Chooser, a PrintMonitor message prompts you to insert an envelope.
7 If you are printing several envelopes, insert the next envelope when the Paper Out light
flashes again.
Do not feed the next envelope before the light prompts you to, or the
envelope may jam.
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