Convinar 2 pdf de 1000 paginas de pares e impares en 1 Solo

If I understand you correctly, you want to insert a single-page file after each page of your PDF, correct?

If so, you can do it using (paid-for) tool I've developed: https://www.try67.com/tool/acrobat-insert-one-pdf-file-into-another-multiple-times

If you want to actually merge two 1000-page files, one with the odd pages and another with the even ones, to a single 2000-page file, you can use this other (also paid-for) tool I've created:

https://www.try67.com/tool/acrobat-combine-even-odd-pages-2018