The documents you submitted on Monday were perfect.
The documents you sent on Monday were perfect.
The documents you handed in on Monday were perfect.
"The documents you submitted on Monday were perfect."
Documents だと複数形なので was ではなく were です。
但し書類が一つの場合は was で良いです。
提出方にも寄りますがメールなどの場合は後者の文章、
直接手渡しされた場合は最後の文章も使えます。