Like CelGn stated, the Apple ImagWriter (1) printer is not parallel. It is serial, using a DB-25 Serial Connector. It looks like a Parallel Connector but it is not. And it cannot connect to AppleTalk/LocalTalk or to a network directly.
Macs (of the time - the 128K to the 512Ke) used DB-9 Serial Ports, and later Macs (Mac Plus, SE, Mac IIs, so on...) used Din-8 Serial Ports. You need the proper cable to connect the Mac to the printer, whether a DB-9 to DB-25 for the older Macs or Din-8 to DB-25.
And like CelGen stated, only the ImageWriter II and the ImageWriter LQ can be connected to a AppleTalk/LocalTalk if and only if it has a AppleTalk Module in its expansion area. Otherwise it was just a Serial Printer like its older brother - The Imagewriter. The ImageWriter II (and the LQ) used the Din-8 connector, so for older Macs you need a DB-9 to Din-8 Cable, and for the newer Macs it's a Din-8 to Din-8 cable. You can not use AppleTalk/LocalTalk Cables to connect to the printer without the AppleTalk Module and think it will work, because it wont.
Depending on the system, you can share the printer. If the printer is on the 512K, I believe you can turn on Printer Sharing on the Chooser and do it that way with the printer on the Mac's Modem Port and the AppleTalk/LocalTalk on the Printer Port to connect to the other Macs. I remember you can on System 6.04 so that Mac 512K needs to be a 512Ke. This is how I did it with my printer on my IIcx (later IIci) with my Duo 210, 2300, and PB5300.
Macs never had a Parallel Port, so that "hard drive" connector on the 512K is the floppy port and is a DB-19. On the Plus, there is a SCSI Port on a DB-25. In most cases you will need a DB-25 to SCSI-50 connector for your SCSI Needs. If you are sharing your hard drive on the Plus to the 512Ke, the hard drive needs to be on the DB 25. Then you need to have AppleShare on in the Plus. AppleShare on System 6 is an extension that needs to be added to the System Folder; it is built-in on System 7, you will need 4MB of RAM for System 7 for the Mac