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

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2010-02-19</periodOfReport>

    <issuer>
        <issuerCik>0000914156</issuerCik>
        <issuerName>UFP TECHNOLOGIES INC</issuerName>
        <issuerTradingSymbol>UFPT</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001240680</rptOwnerCik>
            <rptOwnerName>LESAVOY RICHARD</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O UFP TECHNOLOGIES, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>172 EAST MAIN STREET</rptOwnerStreet2>
            <rptOwnerCity>GEORGETOWN</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>01833</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Vice President</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock, $.01 Par Value</value>
            </securityTitle>
            <transactionDate>
                <value>2010-02-19</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>11792</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>122611</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Represents restricted stock units granted on February 24, 2009, under the issuer's 2003 Incentive Plan subject to satisfaction of performance targets that are to be settled solely in shares of common stock. The transaction date represents the date on which the issuer's Compensation Committee determined the performance targets were achieved. The units vest with respect to one-third of the shares on February 24, 2011 and with respect to an additional one-third on each of February 24, 2012 and 2013, so long as the recipient is in the continuous employ of the Issuer through each such respective vesting date.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>Patrick J. Kinney, Jr. as attorney-in-fact for Richard LeSavoy</signatureName>
        <signatureDate>2010-02-23</signatureDate>
    </ownerSignature>
</ownershipDocument>
