Why this happens
Addo Sign automatically handles large files to ensure reliable email delivery.
If attachments exceed 15 MB, the system converts them into a download link instead of attaching them to the email. Smaller files are sent as attachments as usual.
Additionally, file size increases can occur when documents are digitally signed due to the addition of signature-related data.
Why Does File Size Increase After Digital Signing?
Digital signatures ensure the authenticity and integrity of a document. To achieve this, the signing process embeds additional data into the PDF, including:
Certificates and Tokens: These verify the identity of the signer and the validity of the signature.
Signature Objects: Cryptographic data that ensures the document has not been altered after signing.
Proof Pages: Some tools add a page summarizing the signature details. This additional data is stored within the PDF to comply with technical and legal requirements for digital signatures. As a result, the file size increases, and this increase cannot be reversed without invalidating the signature.
If the total file size exceeds 15 MB, recipients will receive a download link.
The sending process is not blocked, the system automatically adjusts delivery.
Senders should inform recipients that they will receive a link instead of attachments.
⚠️It is not possible to determine the total size of your documents in advance.
When signatures are added, the documents increase in size, and the final size also depends on the number of signers.
This increase occurs because digital signatures embed additional data into the PDF, such as certificates, tokens, and cryptographic signature objects, which ensure the document's authenticity and integrity.
💡Tips for sending large documents:
Check file sizes before sending.
Split large documents into smaller PDFs under 15 MB if attachments are required.
Communicate with recipients that files may be delivered via a download link.
Remember that this behavior is automatic and cannot currently be changed.
Optimize the original document by compressing images and using proper PDF export settings.
Use compression tools to reduce the PDF size before sending it for signing.
Why this matters
Sets correct expectations for senders and recipients.
Reduces confusion about missing attachments.
Helps avoid unnecessary support requests related to email delivery.
✅Summary
When users upload documents with a combined file size greater than 15 MB and select email distribution, the system automatically sends a download link instead of attaching the files.
Users should be aware of this behavior before sending to avoid confusion.