Changing existing cell to annotative

What you need to do is open the cell library directly, like you would open a .dgn. (Make a backup of the file before you go any further) Then open the models dialog box (dark blue icon) and you will see all of the models listed there. Each model is a cell. In the dialog, you will see a column with the annotation scale symbol at the top, which is an "A" with a ruler beneath. For each cell you want to make annotative, left-click in this column and you will see a check mark appear. Save and close the library.

Now after you have done this, place the cells at different annotation scales to see how they react. You will probably find that the scale needs to be adjusted, because these weren't drawn with the intention of being annotative. Re-open the library directly and make your corrections.

Be especially careful of cells that contain text, dimensions, or custom line styles. These may also be annotative, and so now that you are making the cells annotative, the effect on those elements will multiply together and become huge. So you will need to remove the annotation scale from the text and dimensions, and possibly adjust the line style scale. Some helpful keyins you might use to help with this process are "annotationscale select element" and "annotationscale remove". Again, definitely have a backup of the library before you make wholesale changes, it will save you from ripping your hair out. Good luck!

Depending upon how you place the cells, they might still end up non-annotative. InRoads (not OpenRoads) will make cells non-annotative. But I believe the ANNOTATIONSCALE ADD command can reactivate their annotative ability.