Deep Unfolding Networks (DUNs) have emerged as a powerful framework for pansharpening due to their interpretable fusion strategies. However, existing DUNs are limited by their serial iterative architectures, which hinder cross-stage and cross-modal feature interactions at different abstraction levels. This limitation results in insufficient integration of multi-level multimodal features and compromised reconstruction accuracy. To address these challenges, we propose the Unfolding-Associative Encoder-Decoder Network (UED-Net), an innovative framework that iteratively extracts multi-level cross-modal degradation encodings and recursively refines features for cross-stage adaptive aggregation decoding through lightweight processes. Specifically, we first introduce the spatial-spectral encoding module, which progressively and interpretably perceives the hierarchical degradation encoding features of both space and spectrum. Moreover, we develop the unfolding-associative attention module to capture pixel-level attention across stages, thereby leveraging the causal relationships of multi-level features for aggregation during decoding. Meanwhile, we implement a progressive alignment mechanism, which coordinates both feature distribution and alignment of spatial and spectral modalities between iterative stages to facilitate adaptive fusion. These modules enable UED-Net to achieve efficient pansharpening by aggregating multi-level features. Extensive qualitative and quantitative experiments confirm the superiority of UED-Net.