How to handle a large file with a qualified signature? A practical guide

Think qualified signatures only work for simple PDF files? Nothing could be further from the truth. We explain how to sign large files step by step.
Large files vs. qualified signatures - proven ways to SmartSign and SimplySign
3-minute read Updated: August 18, 2026

How to sign large files with a qualified signature?

Archives, videos, CAD projects, multi-page reports - in many companies a „big file” is an everyday occurrence. But what if such a file needs to be signed qualified electronic signature? Rest assured - it is possible. All you need is the right tool. Today, we will show you how to deal with large documents using the proCertum SmartSign i SimplySign - two proven solutions available on podpisano.pl.

proCertum SmartSign - support up to 50MB

This tool from Certum (Asseco) designed for computers and can handle really large files. It supports formats: 

  • CAdES (internal and external),
  • XAdES external
  • PAdes (internal)

How to sign a large file with SmartSign?

  1. Install proCertum SmartSign (preferably integrated with SimplySign Desktop).
  2. Under the tab Settings → select a signature format: CAdES external or XAdES external. (More about signature types in the next article - link)
  3. Add a file or folder to be signed
  4. Click „Sign” → select a certificate → enter a PIN.
  5. Done! You will receive:
    • signed file (CAdES/XAdES),
    • Or two files: original + signature [.sig].

💡 You can immediately verify your signature in the „Verify” tab.

SimplySign - mobile convenience

Do you have a large file, but don't want to install the reader and mess around with configuration? SimplySign is a fully remote solution - it works on:

  • computer (thanks to SimplySign Desktop) - max file size is 50 MB
  • smartphone (mobile app).- for PDF only - max file size up to 20 MB

How does it work?

  • Activate the SimplySign service and install the mobile app.
  • Attach the PDF file of your choice to the signature (on the mobile app) and sign it PINem

or

  • Open SimplySign Desktop → add file → connect token  SimplySign (mobile)
  • Confirm signature with PIN
  • The file is signed - everything takes a few seconds.

When to choose what?

  • A large file, such as an archive with documentation?
    Use SmartSign + CAdES/XAdES external - stable and safe.

  • Want to sign a document on the go, without a reader?
    Choose SimplySign - Works mobile and instantly.

To summarize,

Large files and a qualified signature? No problem.

With the help of the proCertum SmartSign, you can even sign documents the size of the  50 MB.

And if convenience and mobility are important - the SimplySign will give you full freedom to 20 MB.

Both solutions are available on podpisano.pl, where we help you choose the best tool for your needs.

In the next article, we'll explain the difference between an internal signature and an external signature, and the formats in which they appear (PAdES, XAdES, CAdES) and when to choose which one. Join us!

Qualified signatures SimplySign and Certum Mini

If you have any concerns or questions, please contact us

+48 22 417 05 55

We'll answer your questions, find a time that works for you, and match you with an advisor at one of our locations throughout Poland.

You can also write an email from us [email protected]. 

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