roland
If I had looked first I would not have needed to post my question, apologies for that. I found the following post on Superuser about this printer which says it all.
The Brother HL-1110 is a GDI printer. That means that it does not render the page to be printed itself, but gets a bitmap for the entire page from the driver. Since a laser printer prints an entire page at once, it needs internal buffer space to store at lease one page. The HL-1110 has only 1MB of buffer which is just enough to store a full page (A4 or US letter) at 300 DPI. I’d assume that a compression technique is used to store higher resolution bitmaps as well (e.g. 600 DPI). If you have a page bitmap that cannot be compressed well this fails resulting in an “out of memory” error. – dasup Aug 26 ’15 at 16:29
As my pdf files are frequently over 1mb this explains why I cannot print them. Next time I buy a laser printer I’ll make sure it has much more memory and that it us expandable, or that it works in some way by streaming the bitmap between driver and printer to avoid memory limitations.