If you have photoshop, you can open the .ai or .pdf file into Photoshop at your desired size, and THEN export as whatever sized Bitmap file you want.
Did you figure out if there was a solution to this? Or is it merely a limitation of Illustrator ’cause it bothers me too.
Sometimes when creating large banners or signage, it’s easier to just send a flattened TIF to the sign creation software, than it is to try to make sure all the drop shadows and gradients are setup correctly in it…. so it’s nice to work with a 150dpi image actual size. And yeah… I do print at 150dpi.. not 75dpi… For billboards and such it’s not a big deal, but sometimes you are printing large graphics that go on walls that can be within 3 ft from people, and 150dpi is nice, cause it gives you a bit of play incase you need to enlarge it more.
CorelDraw is capable of exporting such files… I have not been able to get Illustrator to do it, since I get the same error message.
The weirdest thing is.. “if” we don’t need to adjust the images or layout from the supplied artwork… although we can’t open an Illustrator File or PDF in Illustrator, and export it as a flattened TIFF… we ARE able to open that Illustrator or PDF file into Photoshop at the desired size/resolution.