<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2026 Workiva-->
<!--r:019f6655-17e5-7712-a541-cf569d750bfa,g:65e33b05-37a1-403e-8b1c-b81c0fe9d26f-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:roleRef roleURI="http://www.unionbankvt.com/role/DocumentInformation" xlink:type="simple" xlink:href="unb-20260715.xsd#DocumentInformation"/>
  <link:presentationLink xlink:role="http://www.unionbankvt.com/role/DocumentInformation" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_dei_CoverAbstract_019f6655-17e5-7f0a-884f-3d26678a0901" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_CoverAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentType_019f6655-17e5-77c9-8082-bab0dd83899c" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_DocumentType"/>
    <link:presentationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019f6655-17e5-7f0a-884f-3d26678a0901" xlink:to="loc_dei_DocumentType_019f6655-17e5-77c9-8082-bab0dd83899c" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_AmendmentFlag_019f6655-17e5-73de-89ae-934b3df8e95e" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_AmendmentFlag"/>
    <link:presentationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019f6655-17e5-7f0a-884f-3d26678a0901" xlink:to="loc_dei_AmendmentFlag_019f6655-17e5-73de-89ae-934b3df8e95e" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentPeriodEndDate_019f6655-17e5-72da-866a-d65b4f539555" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_DocumentPeriodEndDate"/>
    <link:presentationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019f6655-17e5-7f0a-884f-3d26678a0901" xlink:to="loc_dei_DocumentPeriodEndDate_019f6655-17e5-72da-866a-d65b4f539555" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityRegistrantName_019f6655-17e5-7a0d-8e39-41dcfee95007" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityRegistrantName"/>
    <link:presentationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019f6655-17e5-7f0a-884f-3d26678a0901" xlink:to="loc_dei_EntityRegistrantName_019f6655-17e5-7a0d-8e39-41dcfee95007" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCentralIndexKey_019f6655-17e5-7266-9e73-cbd65fcb5f24" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityCentralIndexKey"/>
    <link:presentationArc order="5" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019f6655-17e5-7f0a-884f-3d26678a0901" xlink:to="loc_dei_EntityCentralIndexKey_019f6655-17e5-7266-9e73-cbd65fcb5f24" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityIncorporationStateCountryCode_019f6655-17e5-7ed1-8795-bbde0ef0e840" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityIncorporationStateCountryCode"/>
    <link:presentationArc order="6" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019f6655-17e5-7f0a-884f-3d26678a0901" xlink:to="loc_dei_EntityIncorporationStateCountryCode_019f6655-17e5-7ed1-8795-bbde0ef0e840" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFileNumber_019f6655-17e5-7eaa-8b94-ec5f7336dd0b" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityFileNumber"/>
    <link:presentationArc order="7" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019f6655-17e5-7f0a-884f-3d26678a0901" xlink:to="loc_dei_EntityFileNumber_019f6655-17e5-7eaa-8b94-ec5f7336dd0b" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityTaxIdentificationNumber_019f6655-17e5-7109-8ac5-deb5a3a49718" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityTaxIdentificationNumber"/>
    <link:presentationArc order="8" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019f6655-17e5-7f0a-884f-3d26678a0901" xlink:to="loc_dei_EntityTaxIdentificationNumber_019f6655-17e5-7109-8ac5-deb5a3a49718" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine1_019f6655-17e5-71e4-a97b-8e8fd60f7aa8" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityAddressAddressLine1"/>
    <link:presentationArc order="9" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019f6655-17e5-7f0a-884f-3d26678a0901" xlink:to="loc_dei_EntityAddressAddressLine1_019f6655-17e5-71e4-a97b-8e8fd60f7aa8" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressCityOrTown_019f6655-17e5-71df-a80f-99a59bdc5a66" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityAddressCityOrTown"/>
    <link:presentationArc order="10" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019f6655-17e5-7f0a-884f-3d26678a0901" xlink:to="loc_dei_EntityAddressCityOrTown_019f6655-17e5-71df-a80f-99a59bdc5a66" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressStateOrProvince_019f6655-17e5-720c-be64-a75bcdbbb706" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityAddressStateOrProvince"/>
    <link:presentationArc order="11" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019f6655-17e5-7f0a-884f-3d26678a0901" xlink:to="loc_dei_EntityAddressStateOrProvince_019f6655-17e5-720c-be64-a75bcdbbb706" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressPostalZipCode_019f6655-17e5-79bf-8bdd-f63b150abcea" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityAddressPostalZipCode"/>
    <link:presentationArc order="12" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019f6655-17e5-7f0a-884f-3d26678a0901" xlink:to="loc_dei_EntityAddressPostalZipCode_019f6655-17e5-79bf-8bdd-f63b150abcea" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CityAreaCode_019f6655-17e5-7fd2-8db8-551f5e22dda5" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_CityAreaCode"/>
    <link:presentationArc order="13" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019f6655-17e5-7f0a-884f-3d26678a0901" xlink:to="loc_dei_CityAreaCode_019f6655-17e5-7fd2-8db8-551f5e22dda5" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LocalPhoneNumber_019f6655-17e5-79f4-b8df-31e6a547d1ec" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LocalPhoneNumber"/>
    <link:presentationArc order="14" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019f6655-17e5-7f0a-884f-3d26678a0901" xlink:to="loc_dei_LocalPhoneNumber_019f6655-17e5-79f4-b8df-31e6a547d1ec" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_WrittenCommunications_019f6655-17e5-7e22-9593-0311bacb15fe" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_WrittenCommunications"/>
    <link:presentationArc order="15" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019f6655-17e5-7f0a-884f-3d26678a0901" xlink:to="loc_dei_WrittenCommunications_019f6655-17e5-7e22-9593-0311bacb15fe" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SolicitingMaterial_019f6655-17e5-7947-9fd2-f08ca57aab11" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_SolicitingMaterial"/>
    <link:presentationArc order="16" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019f6655-17e5-7f0a-884f-3d26678a0901" xlink:to="loc_dei_SolicitingMaterial_019f6655-17e5-7947-9fd2-f08ca57aab11" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_PreCommencementTenderOffer_019f6655-17e5-709d-885d-05fd48fe20ed" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_PreCommencementTenderOffer"/>
    <link:presentationArc order="17" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019f6655-17e5-7f0a-884f-3d26678a0901" xlink:to="loc_dei_PreCommencementTenderOffer_019f6655-17e5-709d-885d-05fd48fe20ed" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_PreCommencementIssuerTenderOffer_019f6655-17e5-7b09-a7d5-f3d49676cf2f" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_PreCommencementIssuerTenderOffer"/>
    <link:presentationArc order="18" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019f6655-17e5-7f0a-884f-3d26678a0901" xlink:to="loc_dei_PreCommencementIssuerTenderOffer_019f6655-17e5-7b09-a7d5-f3d49676cf2f" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityEmergingGrowthCompany_019f6655-17e5-7fac-a14b-14a99a7f09d8" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityEmergingGrowthCompany"/>
    <link:presentationArc order="19" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="loc_dei_CoverAbstract_019f6655-17e5-7f0a-884f-3d26678a0901" xlink:to="loc_dei_EntityEmergingGrowthCompany_019f6655-17e5-7fac-a14b-14a99a7f09d8" xlink:type="arc" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
  </link:presentationLink>
</link:linkbase>
