You should define character paragraph in smartform style (eg. H) as BOLD, then parse each TD_LINES-TDLINE, insert characters format at specific place, move it into longer variable and then print.
Example:
TD_LINES-TDLINE =
Adjunto a la presente se serviran encontrar la F:90000157
que ampara 34 procedimientos
After parsing
TDLINE_LONGER =
Adjunto a la presente se serviran encontrar la <H>F:90000157</>
que ampara <H>34</> procedimientos