Upload PDF to a Blob field

Hello
In my database, I have two tables, with blob binary fields, to hold pdf files.
I edit both tables from two forms.
In both forms, I define Document fields (Databases), with the same parameters.
In one, I save the pdf file without problems.
In the other, it records information in binary, so that I cannot recover the original pdf file.
What could be happening to me?
Thank you…