<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2007-08-02</periodOfReport>

    <issuer>
        <issuerCik>0000746598</issuerCik>
        <issuerName>BRADY CORP</issuerName>
        <issuerTradingSymbol>BRC</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001222849</rptOwnerCik>
            <rptOwnerName>JAEHNERT FRANK M</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>6555 WEST GOOD HOPE RD.</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>MILWAUKEE</rptOwnerCity>
            <rptOwnerState>WI</rptOwnerState>
            <rptOwnerZipCode>53223</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>President &amp; CEO</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Class A Common Stock</value>
                <footnoteId id="F5"/>
            </securityTitle>
            <transactionDate>
                <value>2008-02-27</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>.9725</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>30.76</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>3419.7629</value>
                    <footnoteId id="F4"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Deferred Comp. Units</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>30.31</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2008-02-29</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>309.5453</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>30.31</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F1"/>
                <footnoteId id="F3"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F1"/>
                <footnoteId id="F3"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Class A Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>309.5453</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>56722.345</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">The deferred compensation stock units were acquired under the Brady Corporation employee deferred compensation plan and are to be settled in installment payments of Brady's Class A Common Stock upon the persons cessation as an employee of Brady Corporation.</footnote>
        <footnote id="F2">The total shares listed in column 9 represent the aggregate total of the deferred compensation stock units held by the individual as of 2/29/2008 and includes deferred compensation stock units  issued from 8/1/2007 to 2/28/2008 but were inadvertently not previously filed.</footnote>
        <footnote id="F3">This security converts to common stock on 1 for 1 basis.</footnote>
        <footnote id="F4">The total shares listed in Column 5 represent the aggregate total of the non-derivative securities held by the individual as of 2/29/2008. This Form 4 list the correct aggregate total of the non-derivitive securities held by the individual that was reported incorrectly on the  Form 4 filed on 2/29/2008.</footnote>
        <footnote id="F5">This transaction was a result of the employer's 401k payroll deduction plan.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>Barbara Bolens as Attorney-In-Fact</signatureName>
        <signatureDate>2008-03-05</signatureDate>
    </ownerSignature>
</ownershipDocument>
