PackWith’s Board back envelopes are best suitable for string certificates, legal correspondence books, and magazines. Board back envelopes have “please do not bend” text printed by default to secure the documents inside. They are ideal to store photographs, certificates, and official documents. Board back envelopes are available in A3, A4, and A5 sizes that come with peel-and-seal envelopes. Get free delivery in the UK for orders above £20.