Liquid Office uses grayscale colors for white, black and shades of gray. FDFMerge and FDFMerge Lite expect RGB colors only. You can fix this in two ways:

1. Use Liquid Office to change the checkbox backgrounds to transparent or any color but pure white, pure black, or a shade of gray.
2. Using Acrobat, examine the properties of each checkbox field and click Ok. You don’t need to change anything, just click Ok.