Whats The Difference Between a Digitally Signed Plan, Electronic Seal, & Scanned Digital Copy of a Plan?

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Back in the day, kings used wax to seal an envelope to prove its authenticity. That seal evolved over time to become variations of paper embossing and ink ‘wet’ sealing up until this day to certify blueprints by architects and engineers.  In today’s digital world, a more secure solution is needed.

Engineering documents are required to have a proper seal in all states in the US.  Here’s the rule for Florida our native state: FAC 61G15-23.001. Other states follow similar regulations.


The FAX machine used to be the ‘digital’ way to transmit paper from one source to another. Paper was ‘digitized’ and ‘recreated’ after transmission through phone lines.  The recipient might even view the paper file on their computer screens, seeing a ‘digitized’ version of the paper original.

This concept was later refined to allow printers/copiers/scanners to ‘scan’ in the paper copy and create a digital ‘PDF’ or similar file copy.

Keep in mind that in the case of engineering and architectural plans, this is just a ‘digitized’ representation of an originally sealed file, and not a ‘digitally sealed’ set of plans.


A file that is digitally signed (typically used for electronic permitting systems) takes any PDF set of plans, whether it was originally sealed or not, and ‘encodes’ a digitally sealed key onto the PDF.  In the case of digitally sealed plans, half of the key is on the file itself and the other half is typically stored in the cloud in a secure location by a company that has already validated the person signing it.  that person (a licensed engineer or architect in this scenario), has gone through an application and verification process with this approved ‘third party’ validation service and has received not only a password, but in many cases a USB Flash Drive ‘key’ to further authenticate their certification.

These plans can be verified by clicking the blue bar at the top of the real PDF or clicking the digital signature itself and viewing the signer’s information and document properties.  NO BLUE BAR OR VALID SEAL?  It’s not real. The digital signature needs to show as verified by an authorized third party (such as Entrust, Globalsign, or Identrust) and not via a local or unknown source.

Keep in mind each state has its own digital signature requirements which need to be verified before submitting digitally signed plans. That information can be found on each state’s respective board of engineers’ website.

Also, digitally signed documents lock and encode the ‘file’, not each page.  While it is technically possible via special software to put a digital seal on every page, only a single page is required to have the seal as that’s the lock and key for the FILE, not pages.  It’s a different mindset to seeing seals on each page as in the past.  What is possible however is to place a seal ‘stamp’ on each page, then digitally seal the file to lock the integrity.

Remember the rule: Once digital, always digital.  Once hard copy, always hard copy.  Translation:  Digitally sealed plans can only exist as native to digital worlds. Once a hard copy – sealed plan is scanned, that’s not the originally sealed file!

Sometimes, municipalities and reviewing authorities do rely on a paper version of a digitally sealed file and vice versa at some point in their permitting and inspection process, but to be proper the originally certified document must be submitted and use beyond that is verified by the source document (examples include as a product evaluation from ICC, FL, Miami, TDI, or a permit set on record at a building department that’s printed for field convenience).


Some states (such as Florida) must offer a ‘free version’ of a digital seal method to be compliant with their laws.  For this reason, an ‘Electronic Seal’ has been created.  This allows self-signing of a digital file (using Adobe in itself to digitally stamp a plan that’s NOT verified by a third-party).  These electronic, unverified plans need to be accompanied by an affidavit signed, sealed, and scanned by the engineer or architect that proves its authenticity.  More about this can be found in FL at FAC 61G15-23.005 (other states are similar).

This frequently gets confusing for building departments who sometimes still ask for an affidavit even though a true ‘digitally sealed’ version has been presented.  The below helps explain each for Florida.

Also, find below a PDF presentation Engineering Express has made for building officials and has even presented in seminars to municipalities to explain.


Florida Rule (our corporate home) regarding digital signatures can be found by clicking here.  Rules from other states to which our engineers are personally licensed here can be researched online and adopt similar rules.

As of November 2020, the Florida Administrative Code reads for DIGITALLY SEALED PLANS:

61G15-23.004 Procedures for Digitally Signing and Sealing Electronically Transmitted Plans, Specifications, Reports or Other Documents.

(1) Engineering plans, specifications, reports or other documents which must be signed, dated and sealed in accordance with the provisions of section 471.025, F.S., and rule 61G15-23.001, F.A.C., may be signed digitally as provided herein by the professional engineer in responsible charge. As used herein, the terms “certification authority,” and “digital signature” shall have the meanings ascribed to them in sections 668.003(2) and (3), F.S.

(2) A professional engineer utilizing a digital signature to electronically sign and seal engineering plans, specifications, reports or other documents shall have their identity authenticated by a certification authority and shall assure that the digital signature is:  [NOTE BY AUTHOR: DIGITAL SEALS ARE AUTHENTICATED BY A THIRD PARTY AND DON’T NEED AN AFFIDAVIT, THAT’S ONLY IF THIRD PARTY AUTHENTICATION IS NOT USED.  SEE BELOW FOR 61G15-23.005 THAT PERTAINS TO ELECTRONIC VS DIGITAL SEALS]

(a) Unique to the person using it;

(b) Capable of verification;

(c) Under the sole control of the person using it; and,

(d) Linked to a document in such a manner that the digital signature and correspondingly the document is invalidated if any data in the document is changed.

(3) The affixing of a digital signature to engineering plans, specifications, reports or other documents as provided herein shall constitute the signing and sealing of such items.

(a) A digitally created seal as set forth in rule 61G15-23.002, F.A.C., may be placed where it would appear if the item were being physically signed, dated and sealed.

(b) The date that the digital signature was placed into the document must appear on the document in accordance with subsection 61G15-23.001(4), F.A.C., and where it would appear if the item were being physically signed, dated and sealed.

(c) The engineering plans, specifications, reports or other documents being digitally signed and sealed shall include text to indicate the following and place it where an original signature would appear if the item were being physically signed, dated and sealed:

1. The same information required by subsection 61G15-23.002(2), F.A.C., if a digitally created image of the seal is not use;

2. The item has been digitally signed and sealed; and,

3. Printed copies of this document are not considered signed and sealed and all signatures must be verified on any electronic copies.

[excerpt, see the FAC link above for more about the sealed format]


The ELECTRONIC METHOD requires an affidavit that validates the seal in the event there is no third party doing so (like in the digital seal).




Click Here to download our PDF Presentation to building officials regarding digital vs. electronic signatures.

Also, see our page EngineeringExpress.com/Signature for verification of our principal engineer’s signature and more on this rule requirement.

Also, click here to learn how to use certified pre-engineered master plans, TER’s & Evaluation Reports provided by Engineering Express

Last Update: December 15, 2022  

July 24, 2019  Codes & Standards, Company, General  
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