Problems Pasting into acrobat.

I have been editing my book for a month in Acrobat. Publisher sent it to me after layout to edit. For the last month I have been able to make corrections in the original document, copy them and paste them into Acrobat. Sometimes whole chapters have been rewritten and reorganized. I would then strikethrough the old chapter, click on insert or use the yellow stickie and paste it in. Yesterday, that stopped working. I now can paste in about 3 small chapters at a time. Hope someone can help.