I have run this latest document through both Preflight (using the Embed fix) and the PDF Optimizer (which I'm guessing is redundant to some degree?), but the output is still garbled in Firefox. One of the lines becoming garbled still shows this output (via Object Inspector in Acrobat where it looks perfectly fine) --
Filled Text: Constant
ColorSpace: Separation, Black
Color Values = [1.00]
Font: Arial-BoldMT Size: 13.00 Type: OpenType TT
Overprint=True OPM=1 ri=Relative Colorimetric
The only workaround I'm finding (which should hopefully work for the rest of this project although it's cumbersome) is to paste-then-edit from another one of my edited documents that somehow ended up without the MT during one of my edits. I should add that this happens by chance: editing the same headers/text on this same computer in different documents can result in a substitution of Arial _or_ ArialMT -- I'm not sure how it makes the distinction. If I overwrite the font above with, in this case:
Filled Text: Constant
ColorSpace: Separation, Black
Color Values = [1.00]
Font: Arial,Bold Size: 13.00 Type: TrueType
Overprint=True OPM=1 ri=Relative Colorimetric
...then it comes out correctly in Firefox. In Properties, the Arial,Bold shows as an embedded subset while the Arial-BoldMT does not (I'm assuming since my computer doesn't have the font labeled as such? It _will_ let me edit/write in MT which I obviously need to avoid going forward).
Hopefully this provides some clarification. Again, thanks for the help --
Matt