Please sign your forms. Please sign your passports.
So many applications arrive without signatures. These cannot and will not be accepted by the embassies. Your application forms must be signed.
In addition, all of your supporting documents must be signed. We get a lot of letters of invitation which have no signature. A letter of invitation or letter of support must be signed by the invitor. Embassies do not accept unsigned letters as the letetrs just look fake.
So in closing, if the document is not signed, it is not legal. Sign it or have it signed by your supporter or invitor.