Does any one know how to change the line thickness of a already established drawing without having to select each line individually?  I have changed the layer property to the correct thickness using design director, but hat did not change the thickness of existing lines.

Thanks

If you want to use the Layer palette or Design Director to change the Pen Width, the lines should be set to "By Layer". You can use "Select by Entity Type" (Ctrl+T) to select "Line" and whatever else (use the Ctrl or Shift key). If you have more than 100 entities selected, you'll have to use the Selection Info palette or Properties dialog from the Local Menu to change the Pen Width settings, as the Property toolbar may be greyed out.

Does any one know how to change the line thickness of a already established drawing without having to select each line individually?  I have changed the layer property to the correct thickness using design director, but hat did not change the thickness of existing lines.

Thanks

What are the Pen-Widths that you have changed your Layers Pen Widths to?  It isn't until we get up to a certain Pen-Width will the fact that it is "thicker" be apparent and visible to us on a "standard-resolution" screen.
    Example:  I have a "standard-resolution" screen with about 106 pixels-per-inch, and usually use Point units (pt) for Pen-Widths .  If I set my Pen-Width (via the Layers setting or via individual Object's settings) to anything less than 1.5pt, I won't notice any difference in the Pen-Width-- via screen-viewing, not actual printed-to-paper.  ➠ ➠➠ .01pt appears on my monitor-screen the same as 1.4pt.
    If I am recalling correctly, I think there are about 72 Points to an inch.  So, if one is using inches (in or ") for their Pen-Width units, then it wouldn't be until a Pen-Width is set to something greater-than-or-equal-to about 3/144" (0.020833 in) would one be able to actually decipher on their monitor-screen that the Pen-Width is "thicker" than a lower setting.
    Same theory goes with millimeters (mm):  (0.529167 mm).

This is one reason why it is beneficial to print-to-.pdf and/or paper to inspect what your Drawings are going to look like when printed.  After a while-- when using the same Pen-Width units for some time-- you start to develop a sense of what "thickness" all the Pen-Widths are going to appear when printed.

What are the Pen-Widths that you have changed your Layers Pen Widths to?

-Alvin
(I'm not an Expert-guy, so some of what I wrote may be incorrect.  If that's the case, I'm confident an Expert-guy or gal will come along and correct me.)