PDF translation error

Dear Experts ,

I had an issue with the PDF document translation during emailing of PO .The system was generating PDF but while opening the PDF "a drawing error has occured " message has appeared . I was suggested to correct my translation coding . But I am not able to locate the error . Please see the code block as under & suggest me what is wrong ?

LOOP AT i_tline INTO lwa_tline.

TRANSLATE lwa_tline USING ' ~'.

CONCATENATE lv_buffer lwa_tline INTO lv_buffer.

ENDLOOP.

TRANSLATE lv_buffer USING '~ '.

Regards

Anis