Thank you, Dan.
Before I discuss our first quarter financial performance, I'd like to provide an update on the multi-employer pension plans obligation, related to the second quarter 2020 bankruptcy of LSC Communications.
During the first quarter, we successfully negotiated a discounted lumpsum payment with one of the funds, and subsequent to quarter end, we successfully negotiated a discounted lumpsum payment with the second fund. In aggregate, these two funds represented over 57% of the total liability associated with the LSC multi-employer pension plans at the time of the LSC bankruptcy. At the end of the first quarter, our liability was $21.5 million, which included the settlement payments to the two funds, the remaining contingent liability and our estimated share of required payments until final allocation between RRD and DFIN is determined.
As a reminder, DFIN and RRD agreed to share required payments equally and an adjustment and repayments will be made as needed in accordance with the final allocation determined in arbitration. The settlement payments to one of the funds was made in April and our payment to the second fund will be made later in the second quarter, both negatively impacting second quarter cash flow. The expense associated with this liability has been recorded in SG&A within the corporate segment and has been excluded from our non-GAAP results. Relative to our performance in the first quarter, we delivered very strong results, including 11.1% sales growth and significant year-over-year increases in non-GAAP adjusted EBITDA and non-GAAP adjusted earnings per share. We maintain strong market share in our transactional filing business and posted 27.5% growth in our software solution sales, all while continuing to focus on operating efficiencies. These efforts resulted in a non-GAAP adjusted EBITDA margin of 29%, more than doubling the margin from last year's first quarter, further extending the trend in margin improvement we established in the second half of 2019 and demonstrating the strength of our business. On a consolidated basis, net sales for the first quarter of 2021 were $245.3 million, an increase of $24.6 million or 11.1% from the first quarter of 2020.
Software solutions' net sales in the first quarter increased by $13 million or 27.5% compared to the first quarter of 2020, primarily due to accelerated product adoption within Arc Suite, an acceleration of virtual data room activity in Venue, driven by the improved M&A environment, as well as solid subscription growth in ActiveDisclosure. Tech-enabled services net sales increased by $36.6 million or 44.7%, primarily due to increased capital markets transactional activity. Print and distribution revenue decreased by $25 million or 27.3%, primarily due to a regulatory-driven reduction in demand for printed materials within investment companies and less commercial printing where we have proactively exited certain low [Technical Difficulty].
First quarter non-GAAP gross margin was 54.7% or approximately 1,550 basis points higher than the first quarter of 2020, primarily driven by a favorable business mix enjoying growth in higher-margin tech-enabled services and software solution sales combined with lower overall print volume and the impact of ongoing cost control initiatives. Non-GAAP SG&A expense in the quarter was $53 million, $7.9 million higher than the first quarter of 2020.
As a percentage of sales, non-GAAP SG&A was 25.7%, an increase of approximately 70 basis points from the first quarter of 2020. The increase in non-GAAP SG&A is primarily due to sales commission on higher sales, changes in the business mix, higher incentive compensation expense, partially offset by the impact of ongoing cost control initiatives.
Our first quarter non-GAAP adjusted EBITDA was $71.1 million, an increase of $41 million or 136.2% from the first quarter of 2020.
Our first quarter non-GAAP adjusted EBITDA margin was 29%, an increase of 1,540 basis points from the first quarter of 2020, again primarily driven by a favorable sales mix, operating leverage on sales growth, and ongoing cost control initiatives, partially offset by higher incentive compensation and selling expenses.
Turning now to our segment results, net sales in our capital markets software solutions segment were $38.5 million in the first quarter of 2021, an increase of 23.4% from the first quarter of 2020, primarily due to increased Venue virtual data room activity and continued growth in ActiveDisclosure subscriptions. Venue sales increased 30.6% in the first quarter of 2020, driven by an improving M&A environment and sales and marketing efforts focused on gaining market share and accelerating growth, while ActiveDisclosure also had a solid quarter, posting 16% growth. Non-GAAP adjusted EBITDA margin for the segment was 26.8%, an increase of over 1,000 basis points from the first quarter of 2020. The increase in non-GAAP adjusted EBITDA margin was primarily due to the operating leverage benefits on the increased sales, a favorable sales mix as well as the impact of operating efficiencies, partially offset by higher selling expense as a result of increased sales volumes, Net sales in our capital markets compliance and communications management segment were $138.5 million in the first quarter of 2021, an increase of 39.8% from the first quarter of 2020, primarily due to increased capital markets transactional activity continuing the trend that began in the third quarter of 2020. This growth was largely driven by the ongoing momentum in IPO activity as well as M&A activity. The quarter was also significantly impacted by SPAC IPOs, which made up a large share of the total number of priced IPOs in the quarter. Non-GAAP adjusted EBITDA margin for the segment was 43.6%, an increase of over 1,700 basis points from the first quarter of 2020. The large increase in non-GAAP adjusted EBITDA margin was primarily due to operating leverage on the increase in sales, a favorable sales mix and cost control initiatives, partially offset by higher selling expense as a result of the increased sales volume, higher allocation of overhead costs and higher incentive compensation expense. Net sales in our investment company’s software solutions segment were $21.8 million in the first quarter of 2021, an increase of 35.4% from the first quarter of 2020, primarily due to strong demand for ArcDigital, which continues to gain momentum since we launched it in the second quarter of 2020, with new opportunity arising out of the regulatory changes affecting investment companies.
In addition, increased activity from clients adding new funds to ArcPro, also fueled the growth in this segment. Non-GAAP adjusted EBITDA margin for the segment was 25.7%, an increase of 520 basis points from the first quarter of 2020. The large increase in non-GAAP adjusted EBITDA margin was primarily due to operating leverage and the increase in sales and a favorable sales mix, partially offset by higher incentive compensation expense. Net sales in our investment companies compliance and communications management segment were $46.5 million in the first quarter of 2021, a decrease of 37.4% from the first quarter of 2020 due to the impact of regulatory change in investment companies, affecting print-related sales and a reduction of commercial printing sales related to contracts we have proactively exited. Non-GAAP adjusted EBITDA margin for the segment was 15.7%, an increase of 840 basis points from the first quarter of 2020. The increase in non-GAAP adjusted EBITDA margin was primarily due to reduction in overall expense within the segment, primarily due to cost savings as a result of consolidation of the print platform and a lower allocation of overhead costs, which are now being absorbed by our three other operating segments as the lower activity level in this segment results in a reduced need for such shared resources.
Our first quarter 2021 non-GAAP unallocated corporate expenses were $12.5 million, an increase of $2.5 million from the first quarter of last year. The increase in unallocated corporate costs was primarily due to increased incentive compensation, driven by the strong performance, partially offset by the impact of ongoing cost control initiatives. Free cash flow in the quarter was negative $46.3 million, only $2.3 million unfavorable to the first quarter of last year despite an increased level of incentive-based payments in the quarter, including annual bonuses and a 401(k) match based on the strong performance in full year 2020. We ended the quarter with $252.7 million of total debt and $214.2 million of non-GAAP net debt, including $22 million drawn on our revolver. From a liquidity perspective, we had access to the remaining $278 million of our revolver, as well as $38.5 million of cash on hand.
As of March 31, 2021, our non-GAAP net leverage ratio was 1 times, down 1.3 times from the first quarter last year.
As a reminder, our cash flow is historically seasonal.
We are a user of cash in the first quarter, closer to breakeven in the second quarter, and generate more than 100% of our free cash flow in the second half of the year.
As our sales mix continues to evolve to proportionately more subscription-based software solutions, we expect this seasonality to be less significant. We repurchased approximately 127,000 shares of common stock during the quarter for $3.4 million at an average price of $26.92 per share.
We have approximately $46.7 million remaining on our $50 million stock repurchase authorization.
As it relates to the second quarter, transactional activity in capital markets remained robust throughout the month of April. We do expect, however, SPAC activity to reset based on the SEC's recent statement regarding the accounting classification of warrants and their potential action on legal protection for growth projections.
Our expectation is that these actions further legitimize the SPAC market as we currently are supporting our clients in their processes to file revised financial statements and amendments to their SPAC formations and De-SPAC transactions.
Regarding our outlook for the second quarter, we are expecting net sales to be in the range of $230 million to $240 million, down approximately $20 million or 7.5% year-over-year at the mid-point, due to the significant reduction in print and distribution for the regulatory changes related to SEC rules 30e-3 and 498A.
Given the historical seasonality of this print and distribution, the second quarter will include the largest reduction in print sales compared to the other quarters. We remain bullish on the near-term outlook for our software solution sales as well as on capital markets transactional activity. From a profitability perspective, we expect a non-GAAP adjusted EBITDA margin in the mid-20% range similar to last year's second quarter margin. I'll now pass it back to Dan, who will provide an update on our manufacturing platform optimization efforts and cover some first quarter business highlights. Dan?