How to Sign a PDF With an Electronic Signature Online

To sign a PDF with an electronic signature online, simply upload the document to a signing service, select your QES, confirm the signing, and download the completed file.

How to sign a PDF using Vchasno services

The choice of service depends on what exactly you need: to sign a file once, work with documents regularly, or sign them from your smartphone.

Sign a PDF once without registration — Vchasno.Sign

Vchasno.Sign is suitable when you need to quickly sign a PDF online without creating an account. The service is free, and neither you nor the counterparty who will sign the document needs to register.

The service can be used for one-time document signing by individuals, individual entrepreneurs, and legal entities. A compatible valid QES can be used for this.

The process takes just a few clicks: upload the PDF, sign it with your QES, and download the completed document or create a link for the other party.

The signed document can be sent to the counterparty immediately or saved on your device.

Vchasno.Sign is convenient when you need to complete a specific action quickly. However, if you regularly exchange documents with counterparties and want to store them in one place, it is better to choose an electronic document workflow service.

✍️ Sign a PDF without registration.

Regularly exchange and store documents — Vchasno.EDO

Vchasno.EDO is suitable for companies and entrepreneurs who constantly work with electronic documents.

In the service, you can:

• send documents to counterparties;
• sign documents with an electronic signature;
• track document statuses;
• receive signed documents;
• store documents in an electronic archive;
• work with a large document flow;
• sign several documents at once.

This is a convenient option for systematic electronic document workflow when you need not only to apply a signature to a PDF, but to organize the entire document exchange process.

What can be used to sign a PDF

Different types of electronic signatures can be used to sign a PDF. The choice depends on how important the document’s legal significance, signer identification, and protection from changes are.

With a qualified electronic signature

A QES is used to sign legally significant electronic documents. It makes it possible to confirm the signer’s identity and the integrity of the document after signing.

If a document needs to be signed for official exchange with a counterparty, government authority, or another organization, a QES is most often used. Before signing an important document, it is worth checking which type of electronic signature the recipient accepts.

With an advanced electronic signature

An advanced electronic signature can also be used to sign electronic documents in scenarios where this type of signature is accepted by the recipient or by a specific information system.

Before signing an important document, it is worth checking the requirements for the type of signature.

With a drawn signature or an inserted signature image

An image of a handwritten signature inserted into a PDF is not, by itself, a qualified electronic signature.

Such an image does not provide cryptographic verification of the signer’s identity or the integrity of the document. If the document must be legally significant, use the appropriate electronic signature.

What is the most convenient way to sign documents in Vchasno services

For one-time PDF signing, Vchasno.Sign and any valid QES are enough. However, if you regularly sign documents from your smartphone or work from different devices, it is more convenient to use the Vchasno.QES cloud electronic signature.

In what format is a signed PDF stored

When you sign a PDF with a QES, the result may look different depending on the format. In Ukraine, two formats are most commonly used: PAdES and CAdES. Understanding the difference between them will help you avoid disputes with counterparties and tax authorities.

🔐 PAdES: signature inside the PDF

In this case, the signature is embedded directly into the PDF file. You open the document and see the signature panel in a PDF viewer, such as Adobe Reader. There may also be a visual mark, such as a graphic image of the signature, which remains visible when the PDF document is printed. However, the legal force comes not from the graphic image, but from the cryptographic signature data stored inside the document.

This signing method is convenient because all data is stored in one file. If you need to send a document signed in PAdES to a counterparty, it is enough to send only the PDF.

➕ CAdES: PDF and a separate .p7s file

CAdES is the most common format in Ukraine for document exchange through government portals and commercial services. In this case, when you sign a PDF document, the system creates another file, usually a signature file with the .p7s extension. The .p7s file is a “digital fingerprint” confirming that the main document has not been changed after signing.

For the document to have legal force, both files must be stored and transferred together. In other words, to send a signed document to a counterparty, you need to attach both the PDF and the .p7s file. Without the main document, the signature file is just a set of characters.

The main differences between PAdES and CAdES are shown in the table:

Which PDF signing method to choose

If you need to sign one document right now, the easiest option is to use Vchasno.Signature. If you regularly work with electronic documents, sign them from your smartphone, or exchange files with counterparties, it is more convenient to use Vchasno.QES in Vchasno.EDO.

How to verify a signature in a PDF document

In document workflow with partners, it is important not only to choose the right signing format, but also to verify the validity of the electronic signature on an incoming PDF document. This simple procedure takes a couple of minutes and helps protect you from financial and legal risks.

Any file can be verified on the Vchasno.QES service website. Upload the signed document, and the system will automatically determine:

• whether the signer’s full name matches the data in the document;
• whether the certificate was valid at the time of signing;
• whether the data in the document was changed after signing.

If the system displays a “Signature invalid” or “Integrity compromised” notification, the document has no legal force.

How to send a PDF to another party for signing

Sometimes you need not only to sign a document yourself, but also to obtain the counterparty’s signature.

In this case, you can:

1. Upload the PDF to Vchasno.Signature.
2. Apply your signature, if needed.
3. Create a link to the document.
4. Send the link to the counterparty.
5. Check the signing status.

The counterparty can open the link and complete the required action according to the service scenario. They do not need to create an account for this.

This is convenient when you need to quickly organize document signing by another party without exchanging files by email.

The counterparty does not need to create an account to sign a document via a link.

Why a PDF cannot be signed

When working with electronic documents, entrepreneurs and company employees often make mistakes. Let’s look at the most common ones.

The service does not accept the file

Make sure the document is saved in PDF format, opens without errors, and is not damaged. If the file is too large, try reducing its size or exporting the PDF again.

The QES cannot be read

Check whether the signature is valid, whether you selected the correct key, and whether you have access to the password or another method of confirming the signing.

A .p7s file appeared after signing

This may be a normal result of signing in CAdES format. In this case, the .p7s file must be stored together with the original PDF.

The signature became invalid after editing the document

After applying an electronic signature, do not change the signed file. Editing the document may compromise its integrity and make the signature invalid.

If changes need to be made, edit the document, save the new final version, and sign it again.

The counterparty does not see a visual signature

A graphic signature mark and an electronic signature are not the same thing. A document may be cryptographically signed even if there is no signature image on the PDF page.

If it is important for the counterparty to see the signature in the document itself, agree on the signing format in advance.

The wrong version of the document was signed

Before signing, check the file name, date, version, and content.

If you signed the wrong version, do not edit the already signed document. Prepare the correct file and apply the signature again.