Super/subscript output as question marks in Adobe PDF

Dear SAP community members,

We have been working with super and subscript in SAP Business ByDesign and Adobe forms.
The super/subscript numbers (e.g. ₂₃₄₅₆₇₈₉⁴ ⁵ ⁶ ⁷ ⁸ ⁹) are converted correctly on the output on the forms.
The super/subscript alphabet (e.g. xₐ xₑ xₒ xₓ xₔ xₕ xₖ xₗ xₘ xₙ xₚ xₛ xₜ) are not showing correctly and are turned into a "?".

For an example, see the following images: http://imgur.com/a/m2MA1

Please help us solve this issue.

Best Regards,
Joost van Lankveld