Instructions
Weighting
Assess the document to determine if it can be safely unfolded. If it seems brittle, or if the edges are crumbling, the answer is probably no and it should be taken to a professional. However, if it seems strong enough, carefully unfold the document a tiny bit at a time until it's completely flat.
Smooth the document out gently. Place it between two layers of glass and weight the top with a large, heavy book.
Keep it there until the creases are pressed out. Be mindful that this may take a long time. Museum curators sometimes use this conservative method, when appropriate, since it is relatively safe.
Ironing
Carefully unfold the paper according to Step 1 in the "Weighting" section. In fact, if the document is very creased, you might want to try weighting it first before you attempt to iron it. Ironing paper requires a very light touch, and the fewer wrinkles you have to deal with, the better.
Place the document between two pieces of linen, two tea towels, or two pieces of white acid-free paper.
Iron the document gently on very low heat ̵2; no steam ̵2; until the creases are ironed out.