Adobe Digital Editions 4.5.7 for Mac Package Unsigned

The Adobe Digital Editions 4.5.7 for Mac package is not code signed, which makes it difficult to install.  Opening the package on macOS results in the following warning:

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"Digital Editions 4.5 Installer.pkg" can't be opened because it is from an unidentified developer.

Your security preferences allow installation of only apps from the App Store and identified developers.

"Digital Editions 4.5 Installer.pkg" is on the disk image "ADE_4.5_Installer.dmg". Safari downloaded this disk image today at 1:15 PM from www.adobe.com.

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and the only option is to click "OK".  Checking the 4.5.6 and 4.5.7 packages:

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4.5.6

$ pkgutil --check-signature /Volumes/ADE\ 4.5/Digital\ Editions\ 4.5\ Installer.pkg

Package "Digital Editions 4.5 Installer.pkg":

   Status: signed by a certificate trusted by Mac OS X

   Certificate Chain:

    1. Developer ID Installer: Adobe Systems, Inc. (JQ525L2MZD)

       SHA1 fingerprint: F8 32 AC 81 E4 A3 FE A7 19 8E 1C 00 34 A2 F5 B4 F1 A2 BB 55

       -----------------------------------------------------------------------------

    2. Developer ID Certification Authority

       SHA1 fingerprint: 3B 16 6C 3B 7D C4 B7 51 C9 FE 2A FA B9 13 56 41 E3 88 E1 86

       -----------------------------------------------------------------------------

    3. Apple Root CA

       SHA1 fingerprint: 61 1E 5B 66 2C 59 3A 08 FF 58 D1 4A E2 24 52 D1 98 DF 6C 60

4.5.7

$ pkgutil --check-signature /Volumes/ADE\ 4.5/Digital\ Editions\ 4.5\ Installer.pkg

Package "Digital Editions 4.5 Installer.pkg":

   Status: no signature

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Others are experiencing this issue as well:

Error message when downloading Digital Editions 4.5

ADE Installer can't be opened because it is from an unidentified developer

Can the package be properly signed and reuploaded?