I think what don means is that any graphics or text that is unique to each drawing must be placed on the background sheet in the drawing, not as part of the linked object.
This applies whether it's property text or any other type of element.
If you right click in the edge bar you will see 'Insert Symbol As' with a list of options.
One of them is 'Graphics'.
What this will do is insert the graphics of the symbol (lines, text etc.) as graphics in the draft file, just as if you'd drawn them from scratch.
I would suggest that if you must link to another file you only do so for the outline of the drawing border, and any text that never changes. eg. the HEADINGS or LABELS of boxes such as 'Drawn By' or 'Date'.
bc