First of all, you need the temporary document number which can be get either from F-43 itself or from RFDT
table.

In field SRTFD
you should separate it from username.

Then run READ_TEMP_DOCUMENT
FM, after running it you should have your texts in ABAP memory.
To get them use GET_TEXT_MEMORY
.
ls_uf05a-tempd = '0012312356'. "doc number
ls_uf05a-unamd = 'JOHNDOE'. "username
CALL FUNCTION 'READ_TEMP_DOCUMENT'
EXPORTING
I_UF05A = ls_uf05a
TABLES
T_BKPF = lt_bkpf
T_BSEC = lt_bsec
T_BSED = lt_bsed
T_BSEG = lt_bseg
T_BSET = lt_bset
T_BSEZ = lt_bsez
.
DATA: lt_texts TYPE TABLE OF TCATALOG,
t_tline TYPE STANDARD TABLE OF tline,
memory_id(30) VALUE 'SAPLSTXD'.
CALL FUNCTION 'GET_TEXT_MEMORY'
TABLES
TEXT_MEMORY = lt_texts.
READ TABLE lt_texts ASSIGNING FIELD-SYMBOL(<cat>) WITH KEY tdobject = 'BELEG'
tdid = '0001'
tdspras = 'E' BINARY SEARCH.
IF sy-subrc = 0.
memory_id+8(6) = <cat>-id.
ENDIF.
IMPORT tline = t_tline FROM MEMORY ID memory_id.
LOOP AT t_tline ASSIGNING FIELD-SYMBOL(<tline>).
WRITE: <tline>-tdline. "showing the texts
ENDLOOP.