"i might suggest you remove the pages, get some wheat / rice paste ( its just flour and water if you don't want to go full scale archival"
Do no use flour on your work, it has food value that will feed insects and microbes.
What you want is either rice flour STARCH, of better yet, whole wheat Starch.
The process of removing the starch from the flour, includes, at least traditionally, allowing the starch removed from the whole, to ferment mold that, reaches long tendrils down into the vat/bottle, which feed off any non-starch food content, every so often the mold is removed and the cycle continues, until no molds can grow into the now, purified starch.
That leaves you with as archival glue as you may want, especially with thick papers with a border area covered by a 100% rag matboard.
Back the backer board, between the photo and back side, which should be archival quality, with good, glassine acid free paper or glassine border paper and you should have as good a "archival" job as you can get.
By-the-way, serious artists use no only these materials, but acrylic mediums as glues. Unless you want a glued up piece, (two top patches), to be cut off when the work is removed for whatever reason, don't bother using the acrylic.
Actually, there is an acrylic product you could at least use on the backer boards, and be free of the glassine ,Golden Acrylics GAC 100 liquid medium, which has been heavily tested as a barrier, between wood and other discolouring material.
In test of paintings and their supports, wood boards mats, ect, over a seven year period, really significant damage to the painting surface and sub layers, cause by reactions to out gassing, occurred.
In parallel, testing, those boards, etc, that received two or more layers of Gac 100, showed no sign of deterioration, through out-gassing harmful materials.
In other words, try placing light coats of Gac 100 onto the whole side of the backing board, where it meets the photograph, and it will give some protection to your print and 100% rag mats.
I hope this is a help, and remember, using flour will attract critters that like to nibble at you work.
IMO.