*-- Open file which will be used to merge with the file specified in lcPDFFileToAdd
lnResult = iSEDLoadFromFile(lcPDFFile)
lnSelectedDocumentID1 = iSEDSelectedDocument()

lnResult = iSEDLoadFromFile(lcPDFFileToAdd)
lnSelectedDocumentID2 = iSEDSelectedDocument()

*-- Now you simply select the first document, and request that the second document 
*-- be merged to the end of it:

lnResult = iSEDSelectDocument(lnSelectedDocumentID2)
lnResult = iSEDMergeDocument(lnSelectedDocumentID1)

lnResult = iSEDSaveToFile(lcPDFFile)
lnResult = iSEDRemoveDocument(lnSelectedDocumentID2)