With the online service PosteCert, you can read a file directly on the web without having to install any software. To read the file, click on the attachment and choose the .p7m file you want to read. Then, click on the "Verify Signature" button. The activation time for Poste’s digital signature usually takes 3 or 4 working days with standard video identification.
To sign a PDF using SPID Poste, you need to authenticate yourself using your credentials (PosteID enabled with SPID or poste.it) before signing the PDF with SPID Poste. After that, you need to enter your Firma PIN and the OTP verification code (One Time Password), which is sent via SMS to the specified mobile number during enrollment.
To sign a document with a digital signature, click on "Sign" and choose the PDF file format you want to sign. Select the desired type of signature (e.g., .p7m) from the dropdown list. Then, click on "Sign" after entering the smart card PIN. Wait for a response message saying "Document Signed" to indicate the end of the process.
To add a digital signature to a PDF file, open the document or PDF form using Acrobat or Reader. In the right-hand pane, click on "Fill & Sign". Then, in the toolbar, click on the Signature icon. Next, decide whether to add initials or a signature.
I suggest downloading an app like "Visualizzatore fattura elettronica" to open p7m files on an Android smartphone. This free application can be downloaded from the Play Store and other stores. It allows you to view the invoice contained within the XML P7M file.
During a promotional period of six months, the digital signature from Poste Italiane costs 39.04 euros including VAT, and afterward, it costs 45.75 euros including VAT. If you have a verified Poste account or a reliable digital identity, such as PosteID enabled with SPID, you can request it online.
A digital signature requires a support, such as a business key or a smart card, while a remote digital signature does not require dedicated hardware or a smart card.
The signer (the user) clicks on the "SIGN WITH SPID" button (authenticating through their IdP), the Service Provider (SP) sends the document with its seal to the IdP (to verify the signer’s identity), the IdP applies the seal and returns the signed document to the SP after the signer has completed another authentication.
Citizens can sign a document proposed online by an SPID service provider (such as a contract) using this new type of electronic signature simply by authenticating themselves with the SPID identity manager.